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SMITHSONIAN CONTRIBUTIONS TO ZOOLOGY • NUMBER 471

A Phylogenetic Study of the Neotropical Characiform Family Curimatidae (Pisces: Ostariophysi)

Richard P. Vari

SMITHSONIAN INSTITUTION PRESS

Washington, D.C.

1989

ABSTRACT

Vari, Richard P. A Phylogenetic Study of the Neotropical Characiform Family Curimatidae (Pisces: Ostariophysi). Smithsonian Contributions to Zoology, number 471, 71 pages, 45 figures, 3 tables, 1989.—Osteology and soft anatomy of the species of Curimatidae were studied to examine the hypothesis that the family is monophyletic, and to advance a hypothesis of phylogenetic relationships within the family.

Features of the branchial apparatus, buccopharyngeal complex, hyoid arch, jaws, palatine arch, and neurocranium corroborate the monophyly of the Curimatidae. Additional characters in a subset of these systems are congruent with the hypothesis of a sister group relationship between the Curimatidae and Prochilodontidae (Vari, 1983). Shared derived characters of those systems and the antorbital, infraorbitals, opercular apparatus, ligamentum primordiale, hypural complex, caudal-fin rays, proximal pterygiophores of the dorsal fin, laterosensory canal systems of the head and body, and squamation define phylogenetic subunits of the Curimatidae, supporting a phylogenetic hypothesis of four sequential dichotomies and a terminal polychotomy.

I recognize eight genera in the Curimatidae. Curimatopsis, Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, and Curimatella are each hypothesized as monophyletic on the basis of additional shared derived characters. No unique derived characters were found to define the eighth recognized genus, Cyphocharax.

Curimatichthys Fernández-Yépez (1948) is a synonym of Curimatopsis. Potamorhina is redefined to include Gasterotomus Eigenmann (1910), Gasterostomus Fernández-Yépez (1948), Suprasinelepichthys Fernández-Yépez (1948), and Potamorrhina Braga and Azpelicueta (1983). Curimata Bosc (1817) has nine junior synonyms: Semitapicis Eigenmann and Eigenmann (1889b); Peltapleura Fowler (1906); Acuticurimata Fowler (1941); Allenina Fernández-Yépez (1948); Lambepiedra Fernández-Yépez (1948); Bitricarinatra Fernández-Yépez (1948); Bondichthys Whitley (1953); Stupens Whitley (1954); and Semitapiscis Braga and Azpilicueta (1983). Three genera are included in Psectrogaster: Pseudopsectrogaster Fernández-Yépez (1948), Hamatichthys Fernández-Yépez (1948), and Semelcarinata Fernández-Yépez (1948). Rivasella and Curimatorbis, both proposed by Fernández-Yépez (1948), are synonyms of Steindachnerina Fowler (1906). Curimatella has three junior synonyms, all described by Fernández-Yépez (1948): Apolinarella, Walbaunina, and Lepipinna. Cyphocharax has four synonyms: Xyrocharax Fowler (1913b), Hemicurimata Myers (1929), Curimatoides Fowler (1940), and Cruxentina Fernández-Yépez (1948).

The hypothesis of intrafamilial phylogenetic relationships described herein is incongruent, to differing degrees, with classificatory schemes proposed by Eigenmann and Eigenmann (1889b), Eigenmann (1910), Fowler (1975), and Géry (1977b). Numerous differences exist at all taxonomic levels between the scheme of relationships proposed in this study and the “phylogenetic tree” put forward by Fernández-Yépez (1948). Additional hypothesized derived characters described herein are in agreement with the reassignment of Anodus Spix, 1829 (in Spix and Agassiz, 1829) and Eigenmannina Fowler (1906) from the Curimatidae to the Hemiodontidae, first proposed by Roberts (1974) and congruent with results of Vari (1983).

Homoplasious characters are discussed in terms of their overall taxonomic distributions, and relative to their innovative versus reductive natures. Reductive features involving the degree of development of the laterosensory canal system were found to be convergent between Curimatopsis and a subset of Cyphocharax. These paedomorphic features are evidently a consequence of the relative size reduction of these species compared to proximate outgroups.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus).

Library of Congress Cataloging in Publication Data

Vari, Richard P.

A phylogenetic study of the neotropical characiform family Curimatidae (Pisces: Ostariophysi).

(Smithsonian contributions to zoology ; no. 471)

Bibliography: p.

1. Curimatidae—Latin America—Classification. 2. Fishes—Latin America—Classification. I. Title. II. Series.

[QL638.C89V37] 1989 [597′.52] 88-15661

Contents

Introduction

Acknowledgments

Systematic Procedures

Methods and Materials

Terminology

Material Examined

Abbreviations

Character Description and Analysis

Branchial Arches

Dorsal Portion of Branchial Arches

Fourth and Fifth Epibranchials

Fifth Upper Pharyngeal Tooth Plate

Fourth Upper Pharyngeal Tooth Plate and Fourth Infrapharyngobranchial

Third Epibranchial

Third Infrapharyngobranchial

Second Branchial Arch

First Branchial Arch

Ventral Portion of Branchial Arches

First Basibranchial

Second Hypobranchial

Third Hypobranchial

Third Ceratobranchial

Fourth Basibranchial

Fourth Ceratobranchial

Fifth Ceratobranchial

Buccopharyngeal Complex

Hyoid Arch

Urohyal

Basihyal and Basihyal Tooth Plate

Branchiostegal Rays

Antorbital and Infraorbitals

Antorbital

First Infraorbital

Fourth and Fifth Infraorbitals

Sixth Infraorbital

Opercular Apparatus

Opercle and Subopercle

Interopercle

Ligamentum Primordiale

Upper and Lower Jaws

Premaxilla

Maxilla

Dentary

Palatine Arch

Palatine and Ethmo-palatine Cartilage

Ectopterygoid

Mesopterygoid

Metapterygoid

Supraneurals

Caudal Fin Complex

Laterosensory System of Body

Squamation

Synapomorphy List and Phylogenetic Reconstruction

Monophyly of the Curimatidae and Prochilodontidae Clade

Monophyly and Intrafamilial Relationships of the Family Curimatidae

Convergent Characters

Comparisons with Previous Classifications

Resumo

Literature Cited

Requirements for Smithsonian Series Publication

A Phylogenetic Study of the Neotropical Characiform Family Curimatidae (Pisces: Ostariophysi)

Richard P. Vari

____________

Richard P. Vari, Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

Review Chairman: Gary R. Graves, National Museum of Natural History, Smithsonian Institution. Reviewers: Gordon J. Howes, British Museum (Natural History); Lynne R. Parenti, California Academy of Sciences; Stanley H. Weitzman, National Museum of Natural History, Smithsonian Institution.

Introduction

The 100 or more species of the Neotropical characiform family Curimatidae inhabit a broad range of freshwater ecosystems from the still ox-bow lakes, Slow-flowing streams, and meandering rivers typical of lowland floodplains, to swift tributaries and rapids of the Andean piedmont and the uplands of the Guayanan and Brazilian shields. Curimatids are components of the ichthyofauna of trans-Andean Pacific drainages of Central and South America from southern Costa Rica (Bussing, 1966:221) to northern Peru (Eigenmann, 1922:104; Ortega and Vari, 1986:11), and along that versant they also inhabit the Caribbean drainages in northwestern South America (most notably the Río Magdalena system and the Lago Maracaibo drainage basin). Curimatid species occur in the vast portion of South America to the east of the Andes, including the numerous rivers from the Río Orinoco system in Venezuela to south of Buenos Aires, Argentina.

Within this extensive geographic range, the most speciose curimatid fauna is that of the Rio Amazonas basin, inhabited by over 40 curimatid species representing all of the major phyletic lineages of the family. The Río Orinoco and Río Paraguay-Paraná systems include over a dozen species of the family within each of their ichthyofaunas. Less speciose curimatid assemblages are found in Lago Maracaibo, the rivers of the Atlantic Slopes of the Guianas, the rivers of coastal Brazil, Uruguay, and central Argentina, and in the Caribbean and Pacific drainages of trans-Andean South and Central America.

The speciose nature of the Curimatidae is reflected in their variability of overall body size and form. A nearly ten-fold range in standard length (SL) is found between the largest known adult males of Curimatopsis evelynae Géry (ca. 33 mm SL) and the largest reported Curimata mivartii Steindachner (320 mm SL, Dahl, 1971:105). The range in body form within the family is represented at one extreme by elongate fusiform species such as Curimata ocellata Eigenmann and Eigenmann (Figure 1) of the Amazon basin, which schools with and mimics hemiodontids (Géry, 1977a). At the other extreme, Psectrogaster abramoides (Kner) is a deep bodied, laterally compressed species also from the Amazon (Figure 2). The majority of curimatid species cluster around an intermediate, moderately compressed and Slightly elongate body form typified by Curimata incompta Vari (Figure 3), a species endemic to the Río Orinoco system.

Despite the poor representation of some members of the family in systematic collections, many curimatid species occur in large schools (Santos et al., 1985:28–29) that constitute a significant proportion of fish biomass in riverine and lacustrine ecosystems (Lowe-McConnell, 1975:109). In those localities, they exploit the floculent organic material, microdetritus, microvegetation, and filamentous algae typical of most Neotropical aquatic habitats (Carvalho, 1984; Nomura and Hayashi, 1980; Nomura and Taveira, 1979). The populations of numerous curimatid species are particularly concentrated during spawning migrations such as the “piracema” of the Rio Mogi-Guassu of southeastern Brazil (de Godoy, 1975:581–603). These seasonal concentrations permit the ready exploitation of those species by commercial and subsistence fisheries throughout most of the distributional range of the family (Mago-Leccia, 1970:31; Dahl, 1971:105; Rodriquez, 1973; Lowe-McConnell, 1975:74; Saint-Paul and Bayley, 1979:112; Smith, 1981:140; Goulding, 1981:60). Curimatids are also important food items for larger, commercially important, predatory fish species.

FIGURE 1.—Curimata ocellata, USNM 267973, 160.3 mm SL, Brazil, Amazonas, Rio Marauia.

FIGURE 2.—Cyphocharax abramoides, USNM 267952, 105.8 mm SL, Brazil, Pará, Rio Xingu, Belo Monte.

FIGURE 3.—Curimata incompta, USNM 273308, 81.2 mm SL, Venezuela, Estado Bolivar, still back water off Río Orinoco at El Burro.

The diversity of curimatids, particularly the larger species, have been long known to science. More than two centuries ago both Linneaus (1758:312; 1766:514) and Gronovius (1763:123) listed several nominal forms brought to Europe from northeastern South America. Geographically and ecologically more encompassing ichthyological collecting efforts in Neotropical freshwaters since the middle of the eighteenth century have brought curimatids of additional phyletic lineages to the attention of systematists. This greater availability of curimatid specimens from all regions of South America resulted in a progressive increase of described species, with over 120 nominal species or subspecies proposed to date. Associated with the increasingly complex species-level taxonomy were the proposals of numerous genera and subgenera. Despite these efforts, uncertainty continued to pervade curimatid taxonomy at both the specific and supraspecific levels.

The multitude of species level problems within the Curimatidae remained unsettled, partially as a consequence of the absence of a broad overview of the group; most treatments were limited to geographically or politically circumscribed regions. These arbitrary limitations hindered elucidation of species level problems, resolution of which required analysis of geographic and taxonomic samples. The majority of authors were further handicapped by absence of detail in many of the original species descriptions, and by limited collections of comparative materials. These factors, compounded by the large number of nominal species of curimatids, resulted in uncertainty as to the number of recognizable species of curimatids, a poor understanding of the distinguishing characters of the recognizable forms, and confusion as to the geographic distributions of those taxa. Revisionary studies completed (Vari, 1982a,b, 1984a,b, 1987; Vari and Géry, 1985; Vari and Nijssen, 1986) and in progress focus on questions of specific limits and geographic distributions. Such problems are not pursued further in this paper.

Research on the second central problem in curimatid taxonomy, the sequence of evolutionary events within the family, has lagged behind analyses of species-level questions. The relatively few studies that attempted, at least to some degree, to address intra-familial phylogeny failed to clarify our understanding of this core question. Those endeavors (e.g., Fernández-Yépez, 1948) typically made little attempt to critically examine the correlation, or lack thereof, between recognized supraspecific taxa and hypothesized lineages within the family. Rather, these studies usually proposed new genera and subgenera based, either explicitly or by default, on degrees of overall similarity or difference. In retrospect the weakness of such a quasi-phenetic system is reflected both in the erroneous specific and generic synonymizations that riddled the taxonomy of the family, and in the inappropriate assignment of species to supraspecific taxa. These factors led to differing views as to the composition of generic and suprageneric groupings within the Curimatidae.

The generic level subdivision of the family has proceeded in an episodic fashion during the last two centuries. Researchers prior to 1876 typically used Curimatus for the vast majority of curimatids (Curimatus is equivalent to Curimata Bosc, see Opinion 772, International Commission of Zoological Nomenclature, 1966). The only exception was the erroneous utilization of Anodus Spix for some members of the family (e.g., Anodus latior Spix, 1829 (in Spix and Agassiz, 1829) = Potamorhina latior, see Vari, 1984a). As noted by Roberts (1974:429), Anodus is not available in the Curimatidae, being properly applied to two species within the Hemiodontidae (see “Synapomorphy List and Phylogenetic Reconstruction”). Steindachner (1876:81) initiated the valid generic level subdivision of the Curimatidae when he advanced Curimatopsis as a subgenus of Curimata for the first species of curimatid known to retain an incompletely pored laterosensory canal as an adult. Cope (1878:675) continued this trend towards increased generic diversity with his description of the then monotypic genus Potamorhina for the distinctly modified species Curimatus (Anodus) pristigaster previouSly described by Steindachner (1876:73). The number of available nominal genera and subgenera within the family underwent a slow but progressive increase during the next seven decades in the publications of the following authors: Eigenmann and Eigenmann, who proposed Psectrogaster (1889a:7), Curimatella (1889b:415), and Semitapicis (1889b:417); Fowler, who created Cyphocharax, Steindachnerina, Peltapleura (1906:297–300), Xyrocharax (1913b:673), Curimatoides (1940:255), and Acuticurimata (1941:162); Eigenmann (1910:422), who described Gasterotomus; and Myers, (1929:620) who first used Hemicurimata. Fernández-Yépez (1948), in an outburst of generic subdivision, more than doubled the number of nominal genera and subgenera that were available prior to his study. His newly proposed genera (Allenina, Apolinarella, Bitricarinata, Bondia, Camposella, Cruxentina, Curimatichthys, Curimatorbis, Hamatichthys, Lambepiedra, Lepipinna, Pseudocurimata, Pseudopsectogaster, Rivasella, Semelcarinata, Suprasinelepichthys, and Walbaunina) brought the number of generic level names proposed for curimatids to thirty-one. Two of the genera proposed by Fernández-Yépez (1948), Bondia and Camposella, were replaced with Bondichthys and Camposichthys by Whitley (1953:134) who pointed out that they were already occupied in other groups. Camposichthys also proved to be preoccupied, and Whitley (1954:30) put forward Stupens as a substitute.

This trend towards generic level subdivision of the Curimatidae, most notably by Fernández-Yépez (1948), did little to resolve questions of interrelationships within the family at either specific or supraspecific levels. Ten of the twenty-seven genera recognized by Fernández-Yépez were monotypic and could not serve as indicators of phylogenetic relationship. The other more speciose genera proposed or recognized by Fernández-Yépez were nearly always ambiguously defined, with resultant uncertainties about generic limits and species assignment, difficulties previously commented upon by Böhlke (1958:106). Attempts to resolve the problems prevalent in the classification proposed by Fernández-Yépez resulted in the subsequent shifting of species between nominal genera (Böhlke, 1958:108; Ringuelet et al., 1967:198; Britski, 1969:203; Vari, 1982a: 12, 1984a: 11).

Questions of generic diagnosis and inclusiveness aside, we nonetheless find that most authors who proposed classifications for the family or its subunits did so without discussion of the concepts, phenetic or phylogenetic, underlying their schemes. That inexactitude inhibited evaluation of underlying evolutionary patterns hypothesized for the family as a whole or in part, and obscured the degree to which the classifications attempted to reflect a conceptual basis.

The single equivocal exception, the nomenclatural system advanced by Fernández-Yépez and reflected in his “phylogenetic tree” (1948, fig. 12), represented an amalgam of phenetic and quasi-phylogenetic concepts based on a few relatively labile characters analyzed neither in terms of evolutionary polarity nor relative to their utility as indicators of phylogenetic relationship. Indeed Fernández-Yépez's (1948) “phylogenetic tree” is a visual representation of his dichotomous key to the genera of the family rather than a phylogenetic scheme.

The generic level subdivision of the family by Fernández-Yépez (1948), although extreme, nonetheless exemplifies the problems inherent in most classifications of the Curimatidae. Phenetically distinctive species or species groups were typically recognized as separate genera without consideration of the consequence of such actions on the phylogenetic naturalness (sensu Wiley, 1981:71) of previously recognized taxa. Residual species, under such procedures, in most instances formed non-monophyletic generic assemblages not delimited by uniquely derived characters. Rather, those taxa were characterized by combinations of primitive characters (symplesiomorphies) and did not delimit complete evolutionary lineages. As such they did not constitute valid units for comparative studies: morphological, biogeographic, or otherwise.

The studies reported in this paper were undertaken in order to advance a uniform hypothesis of higher level phylogenetic relationships within the Curimatidae based on discrete derived characters. Such a framework will provide a comparative context for future studies of the family, serving as the basis for comprehensive revisionary studies of subunits of the family and analyses of biogeographic patterns within the Curimatidae.

ACKNOWLEDGMENTS.—I am greatly indebted to the following individuals and institutions for the loan and exchange of species, information, and other types of assistance: the late Dr. Donn E. Rosen, Dr. Gareth J. Nelson, and Dr. C. Lavett Smith, American Museum of Natural History (AMNH); Dr. P. Humphry Greenwood and Mr. Gordon J. Howes, British Museum (Natural History) (BMNH); Dr. William Eschmeyer and Ms. Pearl Sonoda, California Academy of Sciences (CAS); Dr. Karel Liem, Dr. William L. Fink, and Mr. Karsten Hartel, Museum of Comparative Zoology; Dr. Naércio Menezes, Dr. Heraldo Britski, and Dr. José Lima de Figueiredo, Museo de Zoologia da Universidade de São Paulo (MZUSP); Dr. Antonio Machado-Allison and Dr. Francisco Mago-Leccia, Museo de Biologia, Universidad Central de Venezuela, Caracas; Dr. Sven O. Kullander, Swedish Museum of Natural History, Stockholm; Prof. Hernán Ortega, Universidad Nacional Mayor de San Marcos, Lima; Dr. Michael Goulding, Museu Paraense “Emilio Goeldi,” Belém; Dr. Gustavo W. Nunan, Museu Nacional, Rio de Janiero; and Dr. Michel Jégu, Instituto Nacional de Pesquisas da Amazônia, Manaus.

Ms. Susan L. Jewett, Mrs. Ann W. Vari, and Mr. Andrew G. Gerberich, National Museum of Natural History, Smithsonian Institution (NMNH), provided technical assistance during the project. Histological preparations of the buccopharyngeal complexes and ligamentum primordiale cartilage body were made by Mrs. Helen Wimer (NMNH). The Portuguese “Resumo” was prepared by Prof. Ricardo M.C. Castro (MZUSP). Figures 1–3 and 28–31 were prepared by Mr. Theophilus B. Griswold (NMNH). The paper benefited from the comments and criticisms of Dr. Stanley H. Weitzman, Dr. Wayne C. Starnes, and Mrs. Ann W. Vari (NMNH), Prof. Ricardo M.C. Castro (MZUSP), Mr. Gordon J. Howes (BMNH), and Dr. Lynne R. Parenti (CAS). I thank all of the above for their assistance and interest.

Research associated with this study was supported in part by the Neotropical Lowland Research Program of the International Environmental Studies Program of the Smithsonian Institution.

Systematic Procedures

Phylogenetic relationships within the Curimatidae are analysed using the methodology of phylogenetic reconstruction, first formalized by Hennig (1950, 1966). The goal of phylogenetic systematics (alternatively termed cladistics or cladism) is the grouping of taxa in series of nested, hierarchical units that reflect the best estimate of their evolutionary history.

Taxa are grouped on the basis of the possession of shared derived characters (synapomorphies). Such characters are considered the only valid basis for cladistic hypotheses of common ancestry. Hypotheses of relationship advanced on the basis of the common possession of shared primitive characters (symplesiomorphies), together with phylogenetic speculations based on concepts of overall phenetic similarity, or degrees of difference are either not useful methods for evaluating alternative phylogenetic hypotheses, or are incongruent with the aims of this study—the advancement of hypotheses of phylogenetic relationships within the Curimatidae. In keeping with the general scientific principle of parsimony, the hypothesis of the phylogenetic history of a group that necessitates the fewest ad hoc assumptions about character transformations is preferred. Here, a computer algorithm, PAUP (Swofford, 1985), is employed to ensure maximum parsimony.

This does not assume that evolutionary mechanisms are necessarily parsimonious, but only that parsimony (simplicity) is the best available inferential principle (Beatty and Fink, 1979; Wiley, 1981). Monophyletic groups are defined as consisting of a hypothesized common ancestor of the lineage and all of its descendants. Traditional alternative definitions of monophyly (see summaries in Wiley, 1981) are of such generality as to include all possible combinations of subunits within a lineage, or are dependent on arbitrary taxonomic ranks, or both, and are therefore often meaningless in application and information content.

Character polarity (plesiomorphy vs. apomorphy; primitive vs. derived) is determined by outgroup comparisons, or via data from ontogenetic transformations, or both. Vari (1983:46–50) suggested that the Curimatidae is the sister group of the Prochilodontidae and the lineage formed by those two families is most closely related to that consisting of the Anostomidae and Chilodontidae. For purposes of character polarity determinations within the Curimatidae, outgroup comparisons are centered first on the Prochilodontidae and then on the Anostomidae and Chilodontidae. Comparisons to other, distantly related, characiform groups, both Neotropical and Old World, were undertaken in instances where outgroup comparisons to the three noted phylogenetically proximate families provided equivocal data on character polarity. Such broader outgroup comparisons were also carried out when the character in question in each of the proximate outgroup taxa was, in turn, uniquely derived relative to the generalized condition of characiforms and thus an inappropriate approximation of the hypothesized plesiomorphous condition of the character for characiformes. Conflicts between polarity decisions based on outgroup comparisons and those arrived at from ontogenetic data are analyzed within the context of the overall phylogeny. Discussions of the theory and methods of character polarity determination can be found in Wiley (1981), Watrous and Wheeler (1981), and Maddison et al. (1984).

Methods and Materials

Osteological and cartilaginous skeletal systems were examined in specimens cleared and counterstained for cartilage and bone with alizarin Red S and alcian blue following the methods outlined by Taylor and Van Dyke (1985). Previously cleared specimens stained solely in alizarin Red S, along with dry skeletal materials, were supplemental sources of osteological data. Anatomical illustrations were prepared using a Zeiss microscopic camera lucida.

TERMINOLOGY.—Myological terminology follows that of Winterbottom (1974). Osteological nomenclature is that of Weitzman (1962) with the following modifications. Vomer is substituted for prevomer, and intercalar for opisthotic. The element traditionally termed the epihyal is instead referred to as the posterior ceratohyal. The ceratohyal of many previous authors is more accurately termed the anterior ceratohyal. This shift in terminology is a consequence of the lack of serial homology between the so-called epihyal and the epibranchials, and the resultant misleading inference of homology inherent in the continued use of epihyal (Nelson, 1969:480–481). The use of epioccipital rather than epiotic follows Patterson (1975). Nelson's substitution (1973) of angulo-articular for articular and retroarticular for angular is more reflective of the homologies of these elements among teleosts than previous terminologies, and is utilized in this paper.

Unless otherwise noted, the concepts of the characiform families used in this paper are those of Greenwood et al. (1966) with three modifications. The Cynodontidae of those authors is considered a tribe in the Characidae rather than a distinct family, in keeping with the results of Howes (1976). The Ichthyboridae of Greenwood et al. (1966) is placed within the Distichodontidae following Vari (1979). Contrary to most previous authors, the Curimatidae of this study does not include the genera Anodus Spix and Eigenmannina Fowler, which are considered to be members of the Hemiodontidae after Roberts (1974). The higher level classification of the Ostariophysi follows Fink and Fink (1981). The nomenclature for the African members of the Characidae is that proposed by Paugy (1984:140–183).

The introductory discussion alluded to the complexity of the taxonomic schemes that have been applied to supraspecific subunits of the Curimatidae. The confusion engendered by the availability of over thirty generic level taxa and eight suprageneric groupings within the family is compounded by questions of species recognizability, errors in the morphological characterization of generic type species by Eigenmann and Eigenmann (1889b) and Fernández-Yépez (1948) (see Vari, 1984a: 13–16, 25), and the presence of a number of undescribed species in the family. The resolution of many of these problems is the subject of revisionary studies published (Vari, 1982a,b, 1984a,b, 1987; Vari and Géry, 1985; Vari and Nijssen, 1986) and in progress. The numerous monotypic genera, many of which will not be recognized when revisionary studies are completed, makes resolution to the level of all nominal genera unproductive. The following discussion therefore deals with what would have constituted multigeneric assemblages under many previous classificatory schemes, particularly that of Fernández-Yépez (1948). The reduced number of recognized groups either represents taxonomic changes already proposed (Vari, 1982a, 1984a), or reflects the likely eventual classificatory schemes that will be proposed on the basis of research in progress. Table 1 lists the generic complexes used in this paper and the nominal genera that each incorporates. The assignment of the nominal species in the Curimatidae to the recognized genera is detailed in Tables 2 and 3. Revisionary studies have been published for two of the clades, Curimatopsis (Vari, 1982a,b) and Potamorhina (Vari, 1984a), and the nomenclature and synonymies of those revisions is followed in this paper. Since such revisions have not yet been published for the other lineages in the family, the discussion of the species in those taxa will be based on all the nominal species assignable to those lineages without prejudging which species will be recognized as valid in future studies.

TABLE 1.—Genera recognized in this study, their included nominal genera, and the type species of those genera. Authors and date of description given for genera and type species of each genus.

Recognized genus

Included nominal genera and their type species

Curimatopsis

Curimatopsis Steindachner, 1876; Curimatus (Curimatopsis) macrolepis Steindachner, 1876

Curimatichthys Fernández-Yépez, 1948; Curimatopsis microlepis Eigenmann and Eigenmann, 1889a

Potamorhina

Potamorhina Cope, 1878; Curimatus (Anodus) pristigaster Steindachner, 1876

Gasterotomus Eigenmann, 1910; Anodus latior Spix, 1829 (in Spix and Agassiz, 1829)

Gasterostomus.—Fernández-Yépez, 1948 [incorrect subsequent spelling of Gasterotomus]

Suprasinelepichthys Fernández Yépez, 1948; Curimatus laticeps Valenciennes, 1849 (in Cuvier and Valenciennes, 1849)

Potamorrhina Braga and Azpelicueta, 1983 [unjustified emendation of Potamorhina]

Curimata

Curimata Bosc, 1817; Salmo edentulous Bloch, 1794

Semitapicis Eigenmann and Eigenmann, 1889b: Charax planirostris Gray, 1854

Peltapleura Fowler, 1906: Salmo cyprinoides Linnaeus, 1766

Acuticurimata Fowler, 1941: Curimatus macrops Eigenmann and Eigenmann, 1889b

Allenina Fernández-Yépez, 1948; Curimata murieli Allen, 1942 (in Eigenmann and Allen, 1942)

Lambepiedra Fernández-Yépez, 1948; Lambepiedra alleni Fernández-Yépez, 1948

Bitricarinata Fernández-Yépez, 1948; Curimatus schomburgkii Günther, 1864

Bondichthys Whitley, 1953; Curimatus mivartii Steindachner, 1878

Stupens Whitley, 1954; Curimatus simulatus Eigenmann and Eigenmann, 1889b

Semitapiscis Braga and Azpelicueta, 1983 [unjustified emendation of Semitapicis].

Psectrogaster

Psectrogaster Eigenmann and Eigenmann, 1889a; Psectrogaster rhomboides Eigenmann and Eigenmann, 1889a

Pseudopsectrogaster Femández-Yépez, 1948; Psectrogaster curviventris Eigenmann and Kennedy, 1903

Hamatichthys Fernández-Yépez, 1948; Anodus ciliatus Müller and Troschel, 1845

Semelcarinata Fernández-Yépez, 1948; Curimatus rutiloides Kner, 1859

Steindachnerina

Steindachnerina Fowler, 1906; Curimatus trachystetus Cope, 1878

Rivasella Fernández-Yépez, 1948; Curimatus melaniris Fowler, 1940

Curimatorbis Fernández-Yépez, 1948; Curimatus atratoensis Eigenmann, 1912b

Pseudocurimata

Pseudocurimata Fernández-Yépez, 1948; Curimatus lineopunctatus Boulenger, 1911

Curimatella

Curimatella Eigenmann and Eigenmann, 1889b; Curiimatus lepidurus Eigenmann and Eigenmann, 1889a

Apolinarella Fernández-Yépez, 1948; Curimatus meyeri Steindachner, 1882a

Walbaunina Fernández-Yépez, 1948; Curimatus dorsalis Eigenmann and Eigenmann, 1889b

Lepipinna Fernández-Yépez, 1948; Anodus alburnus Müller and Troschel, 1845

Cyphocharax

Cyphocharax Fowler, 1906; Curimatus spilurus Günther, 1864

Xyrocharax Fowler, 1913b; Curimata stigmaturus Fowler, 1913b

Hemicurimata Myers, 1929; Curimata esperanzae Myers, 1929

Curimatoides Fowler, 1940; Curimatoides ucayalensis Fowler, 1940

Cruxentina Fernández-Yépez, 1948; Curimata hypostoma hastata Allen, 1942 (in Eigenmann and Allen, 1942)

Each synapomorphy is assigned a number in order to facilitate cross reference between the descriptive text, the listing in “Synapomorphy List and Phylogenetic Reconstruction,” and the cladograms (Figures 44, 45), except that synapomorphies used exclusively within the genus Curimatopsis are assigned letters (A–K), for reasons explained in the text. Synapomorphy numbering is sequential in the final synapomorphy listing rather than in the descriptive text in order to simplify the discussion within “Synapomorphy and Phylogenetic Reconstruction.” The synapomorphies, their polarities, and other comments are described in greatest detail within “Character Description and Analysis.”

TABLE 2.—Genera recognized in this study and their contained nominal species, subspecies, and varieties. Species, subspecies, and varieties are listed chronologically within genera and are cited as in their original descriptions, with authors and dates of description.

Recognized genus

Included species

Curimatopsis

Curimata (Curimatopsis) macrolepis Steindachner, 1876

Curimatopsis microlepis Eigenmann and Eigenmann, 1889a

Curimatopsis macrocephalus Ahl, 1931

Curimatopsis evelynae Géry, 1964a

Curimatopsis crypticus Vari, 1982a

Curimatopsis myersi Vari, 1982b

Potamorhina

Anodus latior Spix, 1829 (in Spix and Agassiz, 1829)

Curimatus laticeps Valenciennes, 1849 (in Cuvier and Valenciennes, 1849)

Curimatus (Anodus) pristigaster Steindachner, 1876

Curimatus altamazonicus Cope, 1878

Semitapiscis squamoralevis Braga and Azpelicueta, 1983

Curimata

Salmo immaculatus Linnaeus, 1758

Salmo cyprinoides Linnaeus, 1766

Salmo edentulus Bloch, 1794

Charax planirostris Gray, 1854

Curimatus vittatus Kner, 1859

Curimatus schomburgkii Günther, 1864

Curimatus asper Günther, 1868

Curimatus knerii Steindachner, 1876

Curimatus mivartii Steindachner, 1878

Curimatus ocellatus Eigenmann and Eigenmann, 1889b

Curimatus simulatus Eigenmann and Eigenmann, 1889b

Curimatus macrops Eigenmann and Eigenmann, 1889b

Curimata copei Fowler, 1906

Curimatus semitaeniatus Steindachner, 1917

Psectrogaster cisandina Allen, 1942 (in Eigenmann and Allen, 1942)

Curimata murieli Allen, 1942 (in Eigenmann and Allen, 1942)

Lambepiedra alleni Fernández-Yépez, 1948

Curimata cerasina Vari, 1984b

Curimata incompta Vari, 1984b

Curimata species A (Vari, in press)

Curimata species B (Vari, in press)

Psectrogaster

Anodus ciliatus Müller and Troschel, 1845

Curimatus rutiloides Kner, 1859

Curimatus essequibensis Günther, 1864

Psectrogaster rhomboides Eigenmann and Eigenmann, 1889a

Psectrogaster amazonica Eigenmann and Eigenmann, 1889a

Curimatus falcatus Eigenmann and Eigenmann, 1889b

Curimatus isognathus Eigenmann and Eigenmann, 1889b

Psectrogaster auratus Gill, 1895

Psectrogaster curviventris Eigenmann and Kennedy, 1903

Curimata pearsoni Myers, 1929

Curimata saguiru Fowler, 1941

Psectrogaster rhomboides australe Risso and Sanchez, 1964

Steindachnerina

Curimatus argenteus Gill, 1858

Curimatus leuciscus Günther, 1868

Curimatus dobula Günther, 1868

Curimatus elegans Steindachner, 1874

Curimatus bimaculatus Steindachner, 1876

Curimatus trachystetus Cope, 1878

Curimatus nasus Steindachner, 1882b

Curimatus hypostoma Boulenger, 1887

Curimatus bimaculatus sialis Eigenmann and Eigenmann, 1889b

Curimatus elegans bahiensis Eigenmann and Eigenmann, 1889b

Curimatus gilberti brevipinnis Eigenmann and Eigenmann, 1889b

Curimatus guntheri Eigenmann and Eigenmann, 1889b

Curimatus conspersus Holmberg, 1891

Curimatus nitens Holmberg, 1891

Curimatus nigrotaenia Boulenger, 1902

Curimatus leuciscus bolivae Eigenmann and Ogle, 1907

Prochilodus stigmaturus Fowler, 1911

Curimatus elegans var. amazonica Steindachner, 1911

Curimatus atratoensis Eigenmann, 1912b

Curimatus issororoensis Eigenmann, 1912a

Curimatus morawhannae Eigenmann, 1912a

Prochilodus pterostigma Fowler, 1913b

Curimatus semiornatus Steindachner, 1914

Curimatus metae Eigenmann, 1922

Curimatus binotatus Pearson, 1924

Curimatus notonotus Miranda Ribeiro, 1937

Curimata melaniris Fowler, 1940

Curimata hypostoma hastata Allen, 1942 (in Eigenmann and Allen, 1942)

Curimatus robustula Allen, 1942 (in Eigenmann and Allen, 1942)

Curimata niceforoi Fowler, 1943

Allenina pectinata Fernández-Yépez, 1948

Cruxentina insculpta Fernández-Yépez, 1948

Curimata fasciata Vari and Géry, 1985

Curimata stigmosa Vari, 1987

Curimata biornata, Braga and Azpelicueta, 1987

Pseudocurimata

Anodus troschelii Günther, 1859

Curimatus boulengeri Eigenmann, 1907 (in Eigenmann and Ogle, 1907)

Curimatus brevipes Eigenmann and Ogle, 1907

Curimatus aureus Pellegrin, 1908

Curimatus lineopunctatus Boulenger, 1911

Curimatus patiae Eigenmann, 1914 (in Eigenmann, Henn, and Wilson, 1914)

Curimatus peruanus Eigenmann, 1922

Curimatella

Anodus alburnus Müller and Troschel, 1845

Curimatus Meyeri Steindachner, 1882b

Curimatus dorsalis Eigenmann and Eigenmann, 1889b

Curimatus lepidurus Eigenmann and Eigenmann, 1889a

Curimatus leucostictus Eigenmann and Eigenmann, 1889b

Curimatus serpae Eigenmann and Eigenmann, 1889a

Curimatus alburnus australe Eigenmann and Kennedy, 1903

Curimatus elegans paraguayensis Eigenmann and Kennedy, 1903

Curimatus (Curimatella) xinguensis Steindachner, 1908

Curimatus (Curimatella) alburnus var. caudimaculata Pellegrin, 1909

Curimatus bolivarensis Steindachner, 1910

Curimata reticulata Allen, 1942 (in Eigenmann and Allen, 1942)

Lepipinna immaculata Fernández-Yépez, 1948

Cyphocharax

Curimata Gilbert Quoy and Gaimard, 1824

Curimatus abramoides Kner, 1859

Curimatus spilurus Günther, 1864

Curimatus voga Hensel, 1869

Curimatus albula Lütken, 1874

Curimatus Magdalenae Steindachner, 1879

Curimatus platanus Günther, 1880

Curimatus Nagelii Steindachner, 1882a

Curimatus microcephalus Eigenmann and Eigenmann, 1889b

Curimatus plumbeus Eigenmann and Eigenmann, 1889b

Curimatus spiluropsis Eigenmann and Eigenmann, 1889b

Curimatus gillii Eigenmann and Kennedy, 1903

Curimatus notatus Steindachner, 1908

Curimatus helleri Steindachner, 1910

Curimatus surinamensis Steindachner, 1910

Curimatus stigmaturus Fowler, 1913b

Curimatus multilineatus Myers, 1927

Curimata esperanze Myers, 1929

Curimatus hermanni Ahl, 1931

Curimatella rehni Fowler, 1932

Curimatopsis saladensis Meinken, 1933

Curimatopsis maculatus Ahl, 1934

Curimatoides ucayalensis Fowler, 1940

Curimatus Vandeli Puyo, 1943

Pseudocurimata grandocule Fernández-Yépez, 1948

Curimatorbis modestus Fernández-Yépez, 1948

Pseudocurimata santacatarinae Fernández-Yépez, 1948

Pseudocurimata steindachneri Fernández-Yépez, 1948

Curimatus (Hemicurimata) esperanzae pijpersi Géry, 1965

Curimata Vanderi Britski, 1980

Curimata punctata Vari and Nijssen, 1986

Curimata spilota Vari, 1987

TABLE 3.—Nominal species within the Curimatidae, their describers and date of description, together with the genera to which they are assigned in this study. Species are arranged alphabetically by specific, subspecific, or varietal epithet, and are cited as in their original description. Undescribed species (e.g., species A, B) are not included.

Species, author, and date of description

Genus

Curimatus abramoides Kner, 1859

Cyphocharax

Curimatus albula Lütken, 1874

Cyphocharax

Anodus alburnus Müller and Troschel, 1845

Curimatella

Lambepiedra alleni Fernández-Yépez, 1948

C.urimata

Curimatus altamazonicus Cope, 1878

Potamorhina

Psectrogaster amazonica Eigenmann and Eigenmann, 1889a

Psectrogaster

Curimatus elegans var. amazonica Steindachner, 1911

Steindachnerina

Curimatus argenteus Gill, 1858

Steindachnerina

Curimatus asper Günther, 1868

Curimata

Curimatus atratoensis Eigenmann, 1912b

Steindachnerina

Psectrogaster auratus Gill, 1895

Psectrogaster

Curimatus aureus Pellegrin, 1908

Pseudocurimata

Curimatella alburnus australe Eigenmann and Kennedy, 1903

Curimatella

Psectrogaster rhomboides australe Risso and Sanchez 1964

Psectrogaster

Curimatus elegans bahiensis Eigenmann and Eigenmann, 1889b

Steindachnerina

Curimatus bimaculatus Steindachner, 1876

Steindachnerina

Curimatus binotatus Pearson, 1924

Steindachnerina

Curimata biornata Braga and Azpelicueta, 1987

Steindachnerina

Curimatus leuciscus bolivae Eigenmann and Ogle, 1907

Steindachnerina

Curimatus bolivarensis Steindachner, 1910

Curimatella

Curimatus boulengeri Eigenmann, 1907 (in Eigenmann and Ogle, 1907)

Pseudocurimata

Curimatus brevipes Eigenmann and Ogle, 1907

Pseudocurimata

Curimatus gilberti brevipinnis Eigenmann and Eigenmann, 1889b

Steindachnerina

Curimatus alburnus var. caudimaculatus Pellegrin, 1909

Curimatella

Curimata cerasina Vari, 1984b

Curimata

Anodus ciliatus Müller and Troschel, 1845

Psectrogaster

Psectrogaster cisandina Allen, 1942 (in Eigenmann and Allen, 1942)

Curimata

Curimatus conspersus Holmberg, 1891

Steindachnerina

Curimata copei Fowler, 1906

Curimata

Curimatopsis crypticus Vari, 1982a

Curimatopsis

Psectrogaster curviventris Eigenmann and Kennedy, 1903

Psectrogaster

Salmo cyprinoides Linnaeus, 1766

Curimata

Curimatus dobula Günther, 1868

Steindachnerina

Curimatus dorsalis Eigenmann and Eigenmann, 1889b

Curimatella

Salmo edentulus Bloch, 1794

Curimata

Curimatus elegans Steindachner, 1874

Steindachnerina

Curimata esperanzae Myers, 1929

Cyphocharax

Curimatus essequibensis Günther, 1864

Psectrogaster

Curimatopsis evelynae Géry, 1964a

Curimatopsis

Curimatus falcatus Eigenmann and Eigenmann, 1889b

Psectrogaster

Species, author, and date of description

Genus

Curimata fasciata Vari and Géry, 1985

Steindachnerina

Curimata Gilbert Quoy and Gaimard, 1824

Cyphocharax

Curimatus gillii Eigenmann and Kennedy, 1903

Cyphocharax

Pseudocurimata grandocule Fernández-Yépez, 1948

Cyphocharax

Curimatus guntheri Eigenmann and Eigenmann, 1889b

Steindachnerina

Curimala hypostoma hastata Allen, 1942 (in Eigenmann and Allen, 1942)

Steindachnerina

Curimatus helleri Steindachner, 1910

Cyphocharax

Curimatus hermanni Ahl, 1931

Cyphocharax

Curimatus hypostoma Boulenger, 1887

Steindachnerina

Lepipinna immaculata Fernández-Yépez, 1948

Curimatella

Salmo immaculatus Linnaeus, 1758

Curimata

Curimata incompta Vari, 1984b

Curimata

Cruxentina insculpta Fernández-Yépez, 1948

Steindachnerina

Curimatus isognathus Eigenmann and Eigenmann, 1889b

Psectrogaster

Curimatus issororoensis Eigenmann, 1912a

Steindachnerina

Curimatus knerii Steindachner, 1876

Curimata

Curimatus laticeps Valenciennes, 1849 (in Cuvier and Valencinnes, 1849)

Potamorhina

Anodus latior Spix, 1829 (in Spix and Agassiz, 1829)

Potamorhina

Curimatus lepidurus Eigenmann and Eigenmann, 1889a

Curimatella

Curimatus leuciscus Günther, 1868a

Steindachnerina

Curimatus leucostictus Eigenmann and Eigenmann, 1889b

Curimatella

Curimatus lineopunctatus Boulenger, 1911

Pseudocurimata

Curimatopsis macrocephalus Ahl, 1931

Curimatopsis

Curimata (Curimatopsis) macrolepis Steindachner, 1876

Curimatopsis

Curimatus macrops Eigenmann and Eigenmann, 1889b

Curimata

Curimatopsis maculatus Ahl, 1934

Cyphocharax

Curimatus Magdalenae Steindachner, 1879

Cyphocharax

Curimata melanira Fowler, 1940

Steindachnerina

Curimatus metae Eigenmann, 1922

Steindachnerina

Curimatus Meyeri Steindachner, 1882b

Curimatella

Curimatus microcephalus Eigenmann and Eigenmann, 1889b

Cyphocharax

Curimatopsis microlepis Eigenmann and Eigenmann, 1889a

Curimatopsis

Curimatus mivartii Steindachner, 1878

Curimata

Curimatorbis modestus Fernández-Yépez, 1948

Cyphocharax

Curimatus morawhannae Eigenmann, 1912a

Steindachnerina

Curimatus multilineatus Myers, 1927

Cyphocharax

Curimata murieli Allen, 1942 (in Eigenmann and Allen, 1942)

Curimata

Curimatopsis myersi Vari, 1982b

Curimatopsis

Curimatus Nagelii Steindachner, 1882a

Cyphocharax

Curimatus nasus Steindachner, 1882b

Steindachnerina

Curimata niceforoi Fowler, 1943

Steindachnerina

Curimatus nigrotaenia Boulenger, 1902

Steindachnerina

Curimatus nitens Holmberg, 1891

Steindachnerina

Curimatus notatus Steindachner, 1908

Cyphocharax

Curimatus notonotus Miranda-Ribiero, 1937

Steindachnerina

Curimatus ocellatus Eigenmann and Eigenmann, 1889b

Curimata

Species, author, and date of description

Genus

Curimatus elegans paraguayensis Eigenmann and Kennedy, 1903

Curimatella

Curimatus patiae Eigenmann, 1914 (in Eigenmann, Henn, and Wilson, 1914)

Pseudocurimata

Curimata pearsoni Myers, 1929

Psectrogaster

Allenina pectinata Fernández-Yépez, 1948

Steindachnerina

Curimatus peruanus Eigenmann, 1922

Pseudocurimata

Curimatus (Hemicurimata) esperanzae pijpersi Géry, 1965

Cyphocharax

Charax planirostris Gray, 1854

Curimata

Curimatus platanus Günther, 1880

Cyphocharax

Curimatus plumbeus Eigenmann and Eigenmann, 1889b

Cyphocharax

Curimatus (Anodus) pristigaster Steindachner, 1876

Potamorhina

Prochilodus pterostigma Fowler, 1913b

Steindachnerina

Curimata punctata Vari and Nijssen, 1986

Cyphocharax

Curimatella rehni Fowler, 1932

Cyphocharax

Curimata reticulata Allen, 1942 (in Eigenmann and Allen, 1942)

Curimatella

Psectrogaster rhomboides Eigenmann and Eigenmann, 1889a

Psectrogaster

Curimata robustula Allen, 1942 (in Eigenmann and Allen, 1942)

Steindachnerina

Curimatus rutiloides Kner, 1859

Psectrogaster

Curimata saguiru Fowler, 1941

Psectrogaster

Curimatopsis saladensis Meinken, 1933

Cyphocharax

Pseudocurimata santacatarinae Fernández-Yépez, 1948

Cyphocharax

Curimatus schomburgkii Günther, 1864

Curimata

Curimatus semiornatus Steindachner, 1914

Steindachnerina

Curimatus semitaeniatus Steindachner, 1917

Curimata

Curimatus serpae Eigenmann and Eigenmann, 1889a

Curimatella

Curimatus bimaculatus sialis Eigenmann and Eigenmann, 1889b

Steindachnerina

Curimatus simulatus Eigenmann and Eigenmann, 1889b

Curimata

Curimata spilota Vari, 1987

Cyphocharax

Curimatus spiluropsis Eigenmann and Eigenmann, 1889b

Cyphocharax

Curimatus spilurus Günther, 1864

Cyphocharax

Semitapiscis squamoralevis Braga and Azpelicueta, 1983

Potamorhina

Pseudocurimata steindachneri Fernández-Yépez, 1948

Cyphocharax

Curimata stigmosa Vari, 1987

Steindachnerina

Prochilodus stigmaturus Fowler, 1911

Steindachnerina

Curimatus stigmaturus Fowler, 1913a

Cyphocharax

Curimatus surinamensis Steindachner, 1910

Cyphocharax

Curimatus trachystetus Cope 1878

Steindachnerina

Anodus troschelii Günther, 1859

Pseudocurimata

Curimatoides ucayalensis Fowler, 1940

Cyphocharax

Curimatus Vandeli Puyo, 1943

Cyphocharax

Curimatus vanderi Britski, 1980

Cyphocharax

Curimatus vittatus Kner, 1859

Curimata

Curimatus voga Hensel, 1869

Cyphocharax

Curimatus (Curimatella) xinguensis Steindachner, 1908

Curimatella

NOTE: Curimatus alberti cited by Günther (1880) and Eigenmann and Eigenmann (1889b) is presumably a lapsus for Cypocharax gilberti (Quoy and Gaimard, 1824). Curimatus hasemanni referred to by Fernández-Yépez (1948:73) is evidently an incorrect citation of Curimatus hermanni Ahl (1931). As noted by Géry (1972:33), Curimatus tigris Fowler (1913a) is actually a member of the Prochilodontidae. Vari and Castro (1988) demonstrate that Prochilodus stigmaturus Fowler (1911) is a species of Steindachnerina.

MATERIAL EXAMINED.—Osteological and myological materials examined are deposited in the following museums: Museo de Biologia, Universidad Central de Venezuela, Caracas (MBUCV); the Museum of Comparative Zoology, Harvard University, Cambridge (MCZ); the Museo de Zoologia da Universidade de São Paulo (MZUSP); and the National Museum of Natural History, Smithsonian Institution, Washington, D.C. (USNM).

The following specimens are the basis for text illustrations or specific observations noted in the text. Measurements, in mm, are of standard length (SL).

ANOSTOMIDAE

Abramites hypselonotus (Günther), USNM 164036; 1 specimen, 100.5 mm; Ecuador, lower Río Bobonaza.

Anostomus plicatus Eigenmann, USNM 225396; 2 specimens, 75.8–95.3 mm; Surinam, Nickerie District, Matappi Creek.

Anostomus species, USNM 231540; 1 specimen, 81.3 mm; no locality data.

Gnathodolus bidens Myers, USNM 231539; 1 specimen, 76.2 mm; aquarium material.

Laemolyta species, USNM 179514; 2 specimens, 75.3–77.0 mm; Brazil, Amazonas, Rio Urubu.

Leporellus vittatus Valenciennes, USNM uncatalogued, 1 specimen, 121.4 mm; Venezuela, Barinas, Río Las Palmas.

Rhytiodus microlepis Kner, USNM 163850; 1 specimen, 131.7 mm; Peru, Loreto, Iquitos.

Schizodon fasciatum Agassiz, USNM 179507; 1 specimen, 49.3 mm; Brazil, Amazonas, Rio Urubu.

Synaptolaemus cingulatus Myers and Fern´ndez-Yépez, MBUCV V-4252; 1 specimen, 71.2 mm; Venezuela, Río Paragua.

CHARACIDAE

Agoniates species, USNM 243222; 1 specimen, 65.6 mm; Brazil, Amazonas, mouth of Rio Iça.

Alestes lateralis Boulenger, USNM 285664; 1 specimen, 75.0 mm; Botswana, Xuguna.

Alestes longipinnis (Günther), USNM 285665; 3 specimens, 44.7–50.5 mm; Togo, Togble-Kope.

Brycon falcatus Müller and Troschel, USNM 226161; 2 specimens, 71.3–78.3 mm; Surinam, Nickerie District, Corantijn River (Figures 6, 18).

Cataprion mento Müller and Troschel, USNM 257547; 1 specimen, 55.2 mm; Venezuela, Estado Apure, Río Cunaviche.

Clupeacharax anchovoides Pearson, USNM 243223; 2 specimens; 57.6–58.7 mm; Peru, Ucayali, Pucallpa.

Exodon paradoxus Müller and Troschel, USNM uncatalogued; 1 specimen, 69.3 mm; Brazil, Goi´s, Rio Tocantins.

Hollandichthys sp., USNM 285668; 3 specimens, 53.5–71.8 mm; no locality data.

Hydrocynus species, USNM 285669; 3 specimens, 38.5–59.2 mm; Volta [Ghana], Black Volta River.

Lepidarchus adonis Roberts, USNM 267290; 5 specimens, 16.8–21.3 mm; Ghana, Aluku.

Phenacogrammus pabrensis Roman, USNM 285666; 2 specimens, 31.0–33.7 mm; Ghana, Dayi River at Vakpo.

CHILODONTIDAE

Caenotropus labyrinthicus (Kner), USNM 231544; 1 specimen. 64.2 mm; Venezuela, Territorio Federal Amazonas, upper Río Orinoco at Tama Tama. Caenotropus labyrinthicus (Kner), USNM 231543; 1 specimen, 58.5 mm; Brazil, Amazonas, Rio Negro.

Caenotropus maculosus (Eigenmann), USNM 231545; 2 specimens, 42.7–46.3 mm; Guyana.

Chilodus punctatus Müller and Troschel, USNM 231542, 13 specimens, 27.1–38.2 mm; Peru, Loreto, Río Nanay.

CITHARINIDAE

Citharinus citharus Geoffroy, USNM 52146; 1 specimen, 218.7 mm; Egypt, Nile River.

CURIMATIDAE

Cyphocharax abramoides (Kner), USNM 267952, 1 specimen, 110.3 mm; Brazil, Pará, Rio Xingu, Belo Monte (Figures 2, 32).

Cyphocharax helleri (Steindachner), USNM 220158; 3 specimens, 48.7–66.3 mm; Surinam, Brokopondo District, Gran Kreek, 63 km from Afobaka.

Cyphocharax magdalenae (Steindachner), USNM 220197; 2 specimens, 78.7–112.3; Panama, Chiriqui, creek 3 mi [4.8 km] W of San Juan on Inter-American Highway.

Cyphocharax microcephala (Eigenmann and Eigenmann), USNM 225307; 2 specimens, 28.7–49.3 mm; Surinam, Nickerie Distict, Kapoeri Creek.

Curimata cisandina (Allen), USNM 229171, 1 specimen, 89.9 mm; Brazil, Amazonas, Rio Solimões, Paraná da Ilha Marchantaria (Figure 19).

Curimata cyprinoides (Linnaeus), USNM 231433; 2 specimens, 17.1–21.4 mm; Surinam, Nickerie District, Corantijn River (Figure 7).

Curimata cyprinoides (Linnaeus), USNM 267964; 1 specimen, 115 mm; Brazil, Amapa, Rio Araguari, Ferreira Gomes (Figures 8, 22, 23, 26C, 27C, 36C, 42D).

Curimata cyprinoides (Linnaeus), USNM 225619; 1 specimen, 79.2 mm; Surinam, Nickerie District, Makilikabroe Creek (Figure 14).

Curimata cyprinoides (Linnaeus), USNM 267963; 2 specimens, 110.5–125.0 mm; Brazil, Pará, Rio Xingu, Belo Monte (Figures 28, 30).

Curimata incompta Vari, USNM 273308; 1 specimen, 81.2 mm; Venezuela, Estado Bolivar, small isolated caño normally draining into Río Orinoco, downstream of El Burro (Figure 3).

Curimata ocellata Eigenmann and Eigenmann, USNM 267973; 1 specimen, 160.3 mm; Brazil, Amazonas, Rio Marauia (Figure 1).

Curimatella alburna (Müller and Troschel), MZUSP 6309; 1 specimen, 98.3 mm; Brazil, Amazonas, mouth of Rio Purus, Lago Castro (Figures 13, 39).

Curimatella meyeri (Steindachner), USNM 261508; 1 specimen, 100.1 mm; Peru, Ucayali, Río Ucayali, Masisea (Figure 35C).

Curimatopsis microlepis Eigenmann and Eigenmann, MZUSP 21053; 1 specimen, 96.0 mm; Brazil, Amazonas, Rio Negro (Figures 5, 15).

Curimatopsis microlepis Eigenmann and Eigenmann, USNM 268867; 1 specimen, 75.8 mm; Brazil, Amazonas, Rio Solimões near Beruri (Figures 12, 22A, 26, 27B, 38A, 39, 40A, 42).

Potamorhina altamazonica (Cope), USNM 257367; 1 specimen, 119.8 mm; Peru, Loreto, Río Amazonas, near Iquitos (Figures 33A, 35B, 36B, 42B).

Potamorhina laticeps (Valenciennes), USNM 121325; 1 specimen, 129.3 mm; Venezuela, Zulia, Lago Maracaibo basin (Figures 10, 22B, 41A).

Potamorhina squamoralevis (Braga and Azpelicueta), USNM 243228; 1 specimen, 90.2 mm; Brazil, Mato Grosso, Baia do Buritizal (Figures 21, 25).

Psectrogaster amazonica Eigenmann and Eigenmann, USNM 261518, 1 specimen, 106.0 mm; Peru, Ucayali, Río Ucayali, Pucallpa (Figures 22C, 36A).

Psectrogaster ciliata (Muüller and Troschel), USNM 269990; 1 specimen, 94.8 mm; Venezuela, Estado Bolivar, small isolated caño normally draining into Río Orinoco, downstream of El Burro (Figures 26B, 38B, 41B, 42C).

Psectrogaster curviventris Eigenmann and Kennedy, USNM 243221; 1 specimen, 72.9 mm; Brazil, Mato Grosso, Baia do Buritizal (Figures 9, 35A).

Pseudocurimata boulengeri (Eigenmann), USNM 285671; 4 specimens, 83.4–92.7 mm; Ecuador, Vinces.

Pseudocurimata lineopunctata (Boulenger), MCZ 54029; 1 specimen, 78.1 mm; Ecuador, Esmeraldas, Estero La Boveda, 4 km from Camerones (Athahualpa).

Pseudocurimata patiae (Eigenmann), USNM 285672; 1 specimen, 82.1 mm; Colombia, Rio Patia, Barbacoas.

Pseudocurimata peruanus (Eigenmann), USNM 285667; 1 specimen, 90.5 mm; Peru, Piura, Tinajones (Figure 43C).

Pseudocurimata troscheli Günther, USNM 285673; 1 specimen, 80.5 mm; Ecuador, Colimes.

Steindachnerina argentea (Gill), USNM 285663; 1 specimen, 83.5 mm; Trinidad, northern Trinidad, Arouca River, just north of Churchill-Roosevelt Highway (Figure 40B).

Steindachnerina bimaculata (Steindachner), USNM 251450; 2 specimens, 61.5–75.4 mm; Peru, Loreto, Río Amazonas, opposite Tabatinga, Brazil (Figures 33B, 34B, 37).

Steindachnerina conspersa (Holmberg), USNM 232224; 1 specimen, 83.2 mm; Paraguay, Presidente Hayes, off Trans-Chaco Highway at km 50 (Figure 36D).

Steindachnerina hypostoma (Boulenger), USNM 167802; 1 specimen, 82.7 mm; Peru, Río Huallaga (Figures 11, 20, 24).

Steindachnerina hypostoma (Boulenger), USNM 261493; 1 specimen, 76.8 mm; Peru, Ucayali, Pucallpa (Figure 29).

Steindachnerina hypostoma (Boulenger), USNM 261513; 1 specimen, 73.4 mm; Peru, Ucayali, Río Ucayali, Pucallpa (Figure 31).

DISTICHODONTIDAE

Mesoborus species, USNM 285674, 1 specimen, 74.5 mm; no locality data.

Nannocharax intermedius Boulenger, USNM 231555; 2 specimens, 50.7–63.4 mm; West Africa.

Paradistichodus dimidiatus Pellegrin, USNM 231556;2 specimens, 45.6–47.3 mm; Ghana, Dayi River.

Xenocharax spilurus Günther, USNM 227693; 1 specimen, 89.3 mm; Gabon, Lac Ezanga (Figure 4).

HEMIODONTIDAE

Anodus elongatus Spix, USNM 231550; 1 specimen, 120.3 mm; Peru, Loreto, Río Ucayali.

Argonectes scapularis Bóhlke and Myers, USNM 243224; 1 specimen, 125.4 mm; Brazil, Amazonas, Río Janauperi.

Bivibranchia bimaculata Vari, USNM 225974; 1 specimen, 97.0 mm; Surinam, Nickerie District, Corantijn River.

Bivibranchia protractila Eigenmann, USNM 194363; 1 specimen, 62.8 mm; Brazil, Mato Grosso, upper Rio Juruena.

Hemiodopsis ocellata Vari, USNM 225593; 1 specimen, 99.6 mm; Surinam, Nickerie District, Corantijn River.

Hemiodus species, USNM 231551; 2 specimens, 55.7–57.1 mm; Brazil, Mato Grosso, Rio Arinos.

Micromischodus sugillatus Roberts, USNM 205527; 1 specimen, 96.1 mm; Brazil, Pará.

HEPSETIDAE

Hepsetus odoe (Bloch), USNM 231553; 1 specimen, 96.2 mm; Togo, Kama.

PARODONTIDAE

Parodon suborbitalis Valenciennes, USNM 231552; 2 specimens, 55.0–58.1 mm; Colombia, Río Salado.

Saccodon dariensis (Meek and Hildebrand), USNM 208505; 1 specimen, 73.3 mm; Panama, Río Membrillo.

PROCHILODONTIDAE

Ichthyoelephas species, USNM 231437; 1 specimen, 110.2 mm; Ecuador.

Prochilodus nigricans Agassiz, USNM 231438; 1 specimen, 144.3 mm; Bolivia, Tumpasa (Figures 6, 16).

Prochilodus rubrotaeniatus Schomburgk, USNM 225419; 1 specimen, 108.7 mm; Surinam, Nickerie District, Corantijn River (Figure 27A).

Semaprochilodus laticeps Steindachner, USNM 270239; 1 specimen, 68.5 mm SL; Venezuela, Estado Bolivar, caño off Río Orinoco at El Burro (Figure 34A).

In addition to the listed specimens, a large number of dry skeletons, stained and cleared glycerine preparations, and alcohol preserved specimens of nearly all species of the family Curimatidae were examined in the comparative studies associated with the present analysis. The majority of those collections are deposited in the collections of the AMNH, MBUCV, MZUSP, and USNM, with lesser numbers of specimens being from the holdings of the other institutions noted under “Acknowledgments.”

ABBREVIATIONS.—The following abbreviations are used in the text and figures.

AA

angulo-articular

AC

anterior ceratohyal

AD

anterodorsal laterosensory canal segment of sixth infraorbital (IO_6)

AE

anterior extension of ventral process of third hypobranchial (H_3)

AI

area of insertion of ligamentum primordiale

ALP

anterior lobulate processes of buccopharyngeal complex

AS

anterior spur of fourth epibranchial (E_4)

ASE_3

anterior articular surface of third epibranchial (E_3)

ASMQF

anterior section of metapterygoid-quadrate fenestra

AVPE_4

anteroventral portion of fourth epibranchial (E_4)

BB

basibranchial (1 to 4)

BC

buccopharyngeal complex

BH

basihyal

BHC

basihyal cartilage

BHTP

basihyal tooth plate

BR

branchiostegal rays (1 to 4)

C

ceratobranchial (1 to 5)

CART

cartilage

CB-LP

cartilage body of ligamentum primordiale

CCH_3

common posterior cartilage of third hypobranchials (H_3)

DCE

distal cartilage of epibranchial (3 or 4)

DEN

dentary

DFPB_3

dorsal flange of third infrapharyngobranchial (PB_3)

DH

dorsal hypophyal

DLF

dorsolateral flange of second infrapharyngobranchial (PB_2)

E

epibranchial (1 to 5)

ECT

ectopterygoid

EPC

ethmopalatine cartilage

FP

first proximal radial pterygiophore of dorsal fin

GA

gill arch

H

hypobranchial (1 to 3)

HC-IO_4

horizontal laterosensory canal of fourth infraorbital (IO_4)

HY

hyomandibula

IL

insertion point of ligament between second and third hypobranchials (H_2 and H_3)

IO

infraorbital (1 to 6)

LF

lateral fold of buccopharyngeal complex

LIG

ligament

LP

ligamentum primordiale

LPE_3

lateral articular process of third epibranchial (E_3)

LR

lateral ridge on dorsal surface of fourth ceratobranchial (C_4)

MBS

medial bony spur of fourth epibranchial (E_4)

MES

mesopterygoid

MET

metapterygoid

METR

metapterygoid ridge

MF

median fleshy fold of buccopharyngeal complex

MPE_3

medial articular process of third epibranchial (E_3)

MPL

mucous producing layer of buccopharyngeal complex

MQF

metapterygoid-quadrate fenestra

MR

medial ridge on dorsal surface of fourth ceratobranchial (C_4)

MVL

mid-ventral ligament

MX

maxilla

N

notch of premaxilla receiving rear portion of premaxilla

NS

neural spines (1 to 7)

PAL

palatine

PB

infrapharyngobranchial (1 to 4)

PC

posterior ceratohyal

PD

posterodorsal laterosensory canal segment of sixth infraorbital (IO_6

PDAS

posterodorsal articular surface of palatine

PE

posterior extension of ventral process of third hypobranchial (H_3)

PLP

posterior lobulate process of buccopharyngeal complex

PMX

premaxilla

POP

preopercle

PP

posterior process of maxilla

PSMQF

posterior section of metapterygoid-quadrate fenestra

QU

quadrate

RA

retroarticular

SF

secondary fleshy folds of buccopharyngeal complex

SN

supraneurals (1 to 6)

SPH

sphenotic

SUOP

supraopercle

SYM

symplectic

TCBB_3

terminal cartilage of third basibranchial (BB_3)

UL

upper lip

UN

uncinate process

UP

upper pharyngeal tooth plate (4 or 5)

VAP

ventral articular process of fourth epibranchial (E_4)

VH

ventral hypohyal

VLF

ventrolateral flange of second infrapharyngobranchial (PB_2)

VPE_4

ventral plate of fourth epibranchial (E_4)

VPH_3

ventral process of third hypobranchial (H_3)

Character Description and Analysis

The primary focus of the present study is the advancement of an explicit hypothesis of the phylogenetic relationships within the Curimatidae. Characters that were discovered to demonstrate phylogenetically significant variation are discussed in this section, along with their taxonomic distributions and the information from outgroup and ontogenetic studies that permits their polarization.

The evidence from the different analyzed characters is brought together under “Synapomorphy List and Phylogenetic Reconstruction” to advance the most parsimonious hypothesis of phylogenetic relationships within the Curimatidae. That hypothesis will, in turn, be used as the basis to evaluate the utility of previous intrafamilial classifications as indicators of the phylogenetic history of the subunits of the family. Since the aim of the present study is the derivation of an hypothesis of the evolutionary history within the Curimatidae, I will not present a detailed description of the osteology and soft anatomy of the involved lineages. Only anatomical systems that show variation relevant to the intrafamilial phylogenetic reconstruction are discussed.

In a few instances, characters pertinent to the question of the monophyly of the lineage formed by the Curimatidae and Prochilodontidae, or relevant to hypotheses proposed in previous studies (Vari, 1982a, 1983, 1984a) are also discussed. Character variation at levels less inclusive than the genus is not usually detailed. Exceptions involve the genera Curimatopsis and Potamorhina which have already been revised (Vari, 1982a and 1984a, respectively) and which were the subjects of associated phylogenetic analyses. Species level relationships within the remaining groups will be analyzed as part of forthcoming revisionary studies.

Among the hypothesized derived characters discovered during this study, some were found to have distributions within the Curimatidae incongruent with the most parsimonious hypothesis of relationships based on the overall distribution of all synapomorphies. Such homoplasies are not recognizable a priori, but can only be identified within the context of the final phylogenetic hypothesis. Homoplasious characters and the degree to which different groups of characters contribute to the final sets of congruent synapomorphies and homoplasies is analyzed in the section “Convergent Characters.” Nonetheless, in order to simplify the discussion, homoplasies and their distributional incongruities relative to the hypothesized phylogeny will also be discussed at appropriate points in this section.

BRANCHIAL ARCHES

The bones, cartilages, and associated connective tissues and muscles of the branchial arches have been a source of considerable morphological information pertinent to the elucidation of the phylogenetic relationships of the Curimatidae. The eight derived branchial basket characters listed by Vari (1983:11–24, 47) for the Curimatidae and Prochilodontidae represent the majority of the hypothesized synapomorphies for that clade. Similarly, half of the characters uniting the lineage consisting of the Curimatidae and Prochilodontidae to the clade formed by the Anostomidae and Chilodontidae are gill arch synapomorphies (Vari, 1983:46–47). Research associated with this study has uncovered an additional derived modification in the dorsal portions of the branchial basket whose phyletic distribution is congruent with a hypothesis of a sister group relationship between the Curimatidae and Prochilodontidae along with three additional synapomorphies for the species of the Curimatidae. This system also demonstrates numerous characters that are informative relative to a hypothesis of generic level relationships within the Curimatidae.

Dorsal Portion of Branchial Arches

The large number of synapomorphies in the bones, cartilages, and ligaments of the dorsal portions of the branchial system within the Curimatidae are discussed below. In order to simplify discussion of the numerous characters found in the multitude of individual elements in that system, the analysis is arranged around subunits of the arches. These subunits typically consist of individual components (e.g., the fourth epibranchial and its associated cartilages and ligaments), although in some situations, functional complexes (e.g., the dorsal portion of a single branchial arch) will be the unit of analysis.

The branchial arches of prochilodontids, the hypothesized sister group to the Curimatidae (Vari, 1983), serve as the best available approximation of the plesiomorphous condition of most components of the branchial system for curimatids. Prochilodontids demonstrate derived gill arch modifications hypothesized as common to the presumed ancestor of that family and the Curimatidae. Apart from those few derived modifications unique to the family, the prochilodontid branchial basket retains overall its hypothesized ancestral condition. The Prochilodontidae demonstrates only one modification of the condition of the upper portion of the gill arches hypothesized as common to the ancestors of prochilodontids and curimatids that is significant for the following discussion. That character involves the form of the fifth upper pharyngeal tooth plate (UP_5). All members of the Prochilodontidae have that element restructured into a vertically expanded, transversely flattened plate, an alteration unique for the members of that family among Characiformes (Vari, 1983:19, 49; Figure 6).

As a consequence of its apomorphous nature, the UP_5 of the Prochilodontidae cannot serve as an approximation of the plesiomorphous condition of that element for comparative studies within the Curimatidae. Rather it is necessary to use more distant outgroups in polarizing character state transition series for that ossification. The sister group to the Prochilodontidae and Curimatidae, the clade formed by the Anostomidae and Chilodontidae, also has the fifth upper pharyngeal tooth plate significantly altered autapomorphously (Vari, 1983:19), making the condition of UP_5 in that lineage similarly inappropriate as an approximation of the plesiomorphous state of the bone in curimatids. Rather it is necessary to refer to phyletically more distant characiform taxa as outgroups. The absence of a definitive hypothesis of a sister group to the lineage formed by the four families (Curimatidae, Prochilodontidae, Anostomidae, and Chilodontidae) obscures the exact outgroup most appropriate for outgroup comparisons to that clade. This ambiguity necessitates reference to all other characiforms as a general outgroup for comparisons involving UP_5.

Fourth and Fifth Epibranchials (E[4], E[5])

Vari (1983:48) listed ten synapomorphies for the members of the Curimatidae (see also “Synapomorphy List and Phylogenetic Reconstruction”). An eleventh shared derived character involving the ventral margin of the fourth epibranchial of curimatids has been found in the morphological studies aimed at deriving a hypothesis of phylogenetic relationships within the family, herein. The anteroventral portion of the fourth epibranchial (AVPE[4], Figure 4) in characiform outgroups extends more ventrally than the remainder of the bone and forms a discrete anteroventral process of the element. That enlarged anterior portion of the bone has two major articular facets. The broad anterior articular surface contacts the posterior portion of the fourth infrapharyngobranchial (PB_4), and the smaller ventral articular surface serves as the region of attachment for the fifth upper pharyngeal tooth plate (UP_5) (e.g., Xenocharax spilurus, Figure 4). The main body of E_4 lies posterior and dorsal of this anteroventral articular portion of the bone, with the two sections of E_4 relatively discrete. The main body of the fourth epibranchial has a transversely rounded ventral margin that is somewhat thickened relative to the plate-like triangular portion of the bone that extends dorsal of it. In curimatids the anteroventral articular portion of the fourth epibranchial and this posterior horizontal ventrally rounded section of the bone are not as discrete as in the outgroups. This fusion, an apomorphous conditon, is the consequence of the presence of an additional transversely flattened vertical plate of bone along the ventral portion of the main body of E_4 (SYNAPOMORPHY 26). That plate (VPE_4 extends along the ventral margin of the main body of E_4 from the posterior surface of the anteroventral articular process of the bone (AVPE_4) (Figure 5). This plate is horizontally elongate overall with a somewhat triangular shape. It is most developed anteriorly where it is continuous along a vertical line with the posterior surface of the articular process of UP_5. The height of the bony plate gradually tapers posteriorly, with the exact form and orientation of the plate in different curimatids a function of the overall morphology of the fourth epibranchial in those lineages.

The main body of the fourth epibranchial also demonstrates a notable degree of phylogenetically informative variability within the Curimatidae. The generalized plan of the bone among prochilodontids serves well as an example of the outgroup condition for the Curimatidae. In prochilodontids the medial surface of the main body of the fourth epibranchial (E_4 in the region dorsal of the area where E_4 articulates with the fifth upper pharyngeal toothplate (UP_5) is flat and unelaborated (Figure 6). The primary axis of the dorsal process of the fourth epibranchial (the dorsal extension of Nelson, 1967, and the suprapharyngobranchial process of Bertmar et al., 1969) in prochilodontids has an anterodorsal orientation. The dorsal process of E_4 in that family terminates dorsally in a transversely flattened cartilage (DCE_4) that is relatively smaller than that in the Curimatidae and widely separated from the uncinate processes of the more anterior epibranchials (e.g., DCE[3], Figure 6). A cord-like ligament (LIG) extends between the posterior surface of the uncinate process of the third epibranchial (E_3) and the main body of the fourth epibranchial (E_4. That inter-epibranchial connective tissue band inserts in prochilodontids onto E_4 slightly posterolateral to the area of articulation of that element with the cartilaginous fourth infrapharyngobranchial (PB[4], Figure 6).

FIGURE 4.—Xenocharax spilurus, USNM 227693, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

Analysis of the conditions of the fourth epibranchial in outgroups to the Curimatidae indicates that the form of the fourth epibranchial described in the preceeding paragraph represents the plesiomorphous state of the ossification. Those cited conditions are hypothesized to have been, in turn, the basis for a number of derived modifications of that ossification in a number of subunits of the Curimatidae.

The medial surfaces of the main body and dorsal process of the fourth epibranchial are unelaborated in all examined characiform outgroups. That simple condition, although also common to all members of the Prochilodontidae (Figure 6), is limited within the Curimatidae to the five species of the genus Curimatopsis (sensu Vari, 1982a,b) (Figure 5). In the genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (Figures 7–11) a distinct posteroventrally sloping, often distally-tapering bony spur (MBS), or a further derived form of such a process, arises from the medial surface of the main body of the fourth epibranchial. The spur extends medially from the body of E_4 to varying degrees towards the midsagital plane, nearly contacting its counterpart of the other side in some subgroups of the family. The unique possession of this medial process of E_4 in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax among the diverse characiform taxa examined is evidence of the derived nature of the possession of the spur. That process is consequently considered a synapomorphy for these seven genera (SYNAPOMORPHY 51). Although prochilodontids have an expansion of the ventral portion of the fourth epibranchial proximate to the cartilaginous articulation of E_4 and UP_5 (VAP, Figure 6), that elaboration differs both in position and form from the spur on the medial surface of the fourth epibranchial in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. The structure in the Prochilodontidae is consequently considered non-homologous with the process in the cited curimatid genera.

FIGURE 5.—Curimatopsis microlepis, MZUSP 21053, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 6.—Prochilodus nigricans, USNM 231438, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

The function of the medial spur arising from the body of the fourth epibranchial of most curimatids is uncertain. Although some connective tissue sheets attach to the spur, neither discrete well-developed ligaments nor muscles arise from that process. The dorsal surface of the spur does, however, contact and conform in shape to the proximate ventral region of the medial and posterior portions of the ventral surface of the muscular epibranchial organ common to all curimatids. Therefore the spur may serve, at least partially, as a support for the large epibranchial organ typical of the family. That functional hypothesis must be qualified by the observation that the Prochilodontidae, the sister group to the Curimatidae, along with the five species of the genus Curimatopsis have well developed epibranchial organs in the absence of a medial spur on the fourth epibranchial. Alternatively, the spur may function to some extent to stiffen a portion of the roof of the pharyngeal cavity. In the intact branchial basket of most curimatids the distal portion of the spur is an integral part of the roof of the pharyngeal cavity and stiffens that muscular tube directly (Potamorhina, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax). In species of Curimata the spur is not directly integrated into the pharyngeal roof but rather supports the fifth upper pharyngeal tooth plate (see discussion below) which is, in turn, incorporated into the fleshy pharyngeal roof. Thus in both conditions the spur functions in reducing the flexibility of the fleshy upper portion of the pharyngeal cavity, a modification that presumably assists in maintaining contact between that region of the pharynx and the opposing dorsal surface of the fifth ceratobranchial during food item manipulation.

This medial bony process of the fourth epibranchial undergoes further apomorphous restructuring in some subgroups of non-Curimatopsis curimatids. These modifications serve to delimit several smaller assemblages within the family. The twelve nominal species assigned to Psectrogaster have the overall form of the medial spur of the fourth epibranchial significantly lengthened posteriorly (Figure 9) relative to the condition in the other members of the family with the structure. The unique nature of the elongation of the spur relative to the medially unelaborated E_4 typical of most characiforms, and with respect to the more moderately developed spur in other non-Curimatopsis curimatids is congruent with the hypothesis of the elongation being a synapomorphy for the species of Psectrogaster (SYNAPOMORPHY 86).

The spur on the fourth epibranchial in the species of Curimata differs from the form of the process in other curimatids in undergoing a progressive ontogenetic expansion ventrally. In the majority of curimatids with a medial spur on E_4 that process has a relatively small base where it arises from the medial surface of the fourth epibranchial. The ventral terminus of the base of the spur, in turn, is distinctly separated from the ventral articular surface of E_4. Similarly the ventral margin of the distal portions of the spur is distinctly separate to varying degrees from the medial margin of the fifth upper pharyngeal tooth plate.

Juveniles of Curimata cyprinoides have a medial spur of the fourth epibranchial with an overall triangular form (Figure 7). At that stage in ontogeny the spur has a moderate area of attachment basally to the articular process of the bone (AVPE_4), a condition similar to that in adults of many non-Curimatopsis curimatids. During development the relatively narrow basal portion of the medial spur characteristic of juveniles of Curimata expands into a broad triangular sheet of bone extending ventrally to the margin of the articular surface between the fourth epibranchial and the fifth upper phargyneal tooth plate (Figure 8). As a consequence the basal portion of the spur in these taxa is continuous along an extensive vertical line with the medial surface of the ventralmost portion of the body of the fourth epibranchial. An additional consequence of that ontogenetic expansion is that specimens of species of Curimata of greater than approximately 40 mm SL have the ventral margin of the medial spur of the fourth epibranchial (MBS) in close proximity to the medial edge of the fifth upper pharyngeal tooth plate (UP_5). These two elements are furthermore relatively tightly attached by a connective tissue sheet. The dorsal margin of the E_4 spur in species of Curimata thickens progressively as the relative overall size of the spur increases; a process that ultimately forms a distinct undercut median shelf at the dorsal margin of the spur in the adults. The expanded median bony spur on E_4 in adults of Curimata is also distinctive in its pronounced fenestration (Figure 8). Neither the dorsomedian shelf nor the fenestration of the fourth epibranchial spur are found in other curimatids.

FIGURE 7.—Curimata cyprinoides, USNM 231433, juvenile, fourth epibranchial and fifth upper pharyngeal tooth plate, right side, medial view, anterior to left, both elements cartilaginous.

FIGURE 8.—Curimata cyprinoides, USNM 267964, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 9.—Psectrogaster curviventris, USNM 243221, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 10.—Potamorhina laticeps, USNM 121325, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 11.—Steindachnerina hypostoma, USNM 167802, dorsal portion of gill arches, right side, medial view, anterior to left (dense patterned stippling represents cartilage).

The ontogenetic restructuring of the E_4 spur of Curimata from a condition comparable to that generalized for spur-bearing curimatids to the triangular plate characteristic of the genus is congruent with a hypothesis of the derived nature of that ossification (SYNAPOMORPHY 78). Similarly the development of a distinct dorsomedial shelf on the medial spur of the fourth epibranchial, and the fenestration of the spur are considered synapomorphous for the genus (SYNAPOMORPHY 79). Those ontogenetically derived polarity hypotheses are furthermore in agreement with data from outgroup analysis which also indicates that the possession of such elaborations of the fourth epibranchial spur are unique to, and represent synapomorphies for, the species of Curimata.

Apomorphous alterations of the dorsal portions of the fourth epibranchial, both ossified and cartilaginous, are notable within the Curimatidae. The form and orientation of the dorsal process of the fourth epibranchial generalized for, and hypothesized as primitive, within the Characiformes is a transversely flattened plate with a vertically or nearly vertically oriented central axis (Figure 4; Vari, 1983, fig. 15). Members of the Curimatidae (Figures 5, 7–11) and Prochilodontidae (Figure 6) are characterized by having that primary axis of the dorsal process of E_4 reoriented anterodorsally to some degree. That reorientation, apomorphous for the two-family clade (SYNAPOMORPHY 1), is least pronounced in the Prochilodontidae, but is more developed in some groups of curimatids as will be discussed below. The distal cartilaginous portion of the fourth epibranchial also varies in morphology within the Curimatidae. Outgroup studies indicate that the cartilage capping the dorsal process of E_4 is primitively a relatively small body as typified by the condition in Xenocharax Günther (Figure 4) and Brycon Müller and Troschel (Vari, 1983, fig. 15). That cartilage body on E_4 in the Prochilodontidae is somewhat, but not markedly, realigned anterodorsally relative to the condition in most characiforms. That shift and the comparable condition and more pronounced realignments within the Curimatidae together represent a synapomorphy for the Curimatidae and Prochilodontidae (SYNAPOMORPHY 2).

Within the Curimatidae further modifications are found both in the overall form of the dorsal process of E_4 and in the alignment and shape of its associated distal cartilage. The species of Curimatopsis are characterized by a distal cartilage of the fourth epibranchial that is similar in form to that in the Prochilodontidae; however, that genus has the primitively dorsal process of the fourth epibranchial more anterodorsally directed than in prochilodontids (Figure 5). That apomorphous anterodorsal reorientation of the dorsal process of E_4 is more pronounced in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. Those taxa have the primitively dorsal process of E_4 more anteriorly directed (Figures 8–11) than in either the Prochilodontidae (Figure 6) or Curimatopsis (Figure 5). As a consequence of this apomorphous reorientation, the transversely flattened cartilaginous terminal portion of the fourth epibranchial (DCE_4) constitutes the anterior limit of that element in non-Curimatopsis curimatids contrary to its dorsal location on the fourth epibranchial that is typical for characiforms. Congruent with the reorientation of the dorsal portion of E_4 is the anterior expansion of the distal cartilage on that element (DCE_4) into an elongate plate. In different phyletic lineages within the Curimatidae that plate extends anteriorly to varying degrees dorsal of the fourth infrapharyngobranchial and above the portions of the other gill arch elements located along the median margin of the dorsal half of the branchial complex (Figures 8, 9, 10, 12, 13).

The absence of comparable modifications of the primitively dorsal process of the fourth epibranchial and its associated terminal cartilage in characiform outgroups is congruent with the hypothesis that these alterations are shared derived characters for the Curimatidae and its subunits at two levels of generality. The moderate degree of anterodorsal alignment of the primary axis of the process in Curimatopsis, and the further derived more anterior alignment of the process in other curimatids together constitute a synapomorphy for the entire family (SYNAPOMORPHY 27). The pronounced anterior realignment, the more derived condition, in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is a derived synapomorphy of lesser generality within the family (SYNAPOMORPHY 52). The latter organization of the ossified and cartilaginous portions of E_4 is considered the condition from which further modifications of the fourth epibranchial in several less inclusive subunits of the Curimatidae are derived.

Among the species of Potamorhina the anteriorly reoriented dorsal process of the fourth epibranchial common to non-Curimatopsis curimatids is apomorphously further lengthened to a significant degree. This elaboration of the process results in a horizontally markedly elongate, vertical wall that extends medially along the anterolateral portion of the muscular epibranchial organ (Figure 10). The transversely-flattened cartilage (DCE_4) that caps the primitively dorsal, now anterior, portion of the bone is congruently significantly lengthened longitudinally in Potamorhina, and extends forward to contact the dorsal margin of the cartilage that caps the uncinate process of the third epibranchial (DCE_3). A distinct separation of these two cartilage bodies typifies other examined characiforms both outside of the Curimatidae (e.g.,Xenocharax spilurus and Prochilodus nigricans, Figures 4, 6), and within the family (Figures 5, 8, 9, 11). The anterior lengthening of the dorsal process of the fourth epibranchial along with the close association of the cartilages of the third and fourth epibranchials in Potamorhina is consequently hypothesized to be synapomorphous for the members of the genus (SYNAPOMORPHIES 64 and 65).

The overall elongation of the fourth epibranchial in Potamorhina is paralleled by the anterior lengthening of the fifth epibranchial in the members of the genus. The fifth epibranchial (E_5) in most characiforms is typically a small cartilage at the posterior corner of the fourth epibranchial lying immediately posterodorsal of the junction of that element and the fourth ceratobranchial (e.g., Xenocharax spilurus, Figure 4). Both prochilodontids and curimatids have the cartilaginous E_5) expanded into a relatively large mass incorporated into the lateral wall of the large epibranchial organ. As noted by Vari (1983) the fifth epibranchial in those families is also noteworthy in its attachment to the posterodorsal margin of the fourth epibranchial, with a resultant encirclement by those elements of the fifth efferent branchial artery. Together this complex is considered a synapomorphy for the Curimatidae and Prochilodontidae (SYNAPOMORPHY 2). Within the Curimatidae the fifth epibranchial in Potamorhina (E[5], Figure 10) is further lengthened beyond the condition in prochilodontids and other curimatids into a long tapering body extending anteriorly to the level of the middle or posterior portion of the fourth infrapharyngobranchial, a synapomorphy unique to members of that genus (SYNAPOMORPHY 70).

All of the diverse groups of characiforms examined in the present study have a distinct cord-like ligament (LIG) that extends posteriorly from the rear margin of the uncinate process of the third epibranchial (E_3) to an attachment on the fourth epibranchial (E_4) (e.g., Xenocharax spilurus and Prochilodus nigricans, Figures 4, 6). This inter-epibranchial ligament attaches to E_4 at the anteriormost limit of the distinct ridge that extends along the lateral surface of the main body of the fourth epibranchial. In most characiforms that ridge on the fourth epibranchial terminates anteriorly just dorsal of the vertical plane through the area of contact of the fourth infrapharyngobranchial (PB_4) and the fourth epibranchial (Figure 12). The exact function of this inter-epibranchial ligament is uncertain, but it apparently limits the degree of flexure of the fourth epibranchial relative to the more anterior arches of the branchial apparatus, and is one of a series of comparable ligaments in the dorsal portion of the gill arches. Shorter, possibly serially homologous, ligaments also extend between the first epibranchial and the second infrapharyngobranchial, and between the second epibranchial and the third infrapharyngobranchial.

The five species of Curimatopsis have the ligament between the third and fourth epibanchials attached onto the relatively short ridge located on the anterolateral surface of the fourth epibranchial, an attachment comparable to the condition described above for characiform outgroups (Figure 12). The species of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax rather than retaining a direct attachment of the ligament onto the main body of the fourth epibranchial have that band inserting onto a bony spur-like process (AS) that extends forward from the anterior margin of the main body of E_4 (Figures 8, 10, 11, 13, 14). The base of this bony spur corresponds in position to the region of E_4 where the E_3-E_4 ligament attaches in other characiforms. The spur, in turn, is longitudinally aligned along the axis of the ligament. Although the degree of development of the spur varies among those curimatids characterized by that process, the common possession of such an anterior extension of E_4 associated with the E_3-E_4 ligament is hypothesized to be a synapomorphy for the genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax given the absence of such an elaboration in examined outgroups (SYNAPOMORPHY 53).

FIGURE 12.—Curimatopsis microlepis, USNM 268867, dorsal portion of third and fourth gill arches, left side, dorsolateral view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 13.—Curimatella alburna, MZUSP 6309, dorsal portion of third and fourth gill arches, left side, dorsolateral view, anterior to left (dense patterned stippling represents cartilage).

Finally the overall form of the ventral portion of the fourth epibranchial is modified in all species of Curimata. In other curimatids, the portion of the fourth epibranchial that articulates with and supports UP_5 is situated directly ventral of the main body of E_4, and is in line with the vertical axis through the dorsal process of that element. In species of Curimata, alternatively, the ventral portion of E_4 is further shifted medially which results in an associated move towards the median plane of the attached fifth upper pharyngeal tooth plate (UP_5). As a consequence of this restructuring the complex consisting of the ventral portion of E_4 and the associated UP_5 in Curimata is located distinctly medial of the primary vertical plane through the dorsal section of the branchial apparatus (Figure 14) (SYNAPOMORPHY 80).

Fifth Upper Pharyngeal Tooth Plate (UP[5])

The ventral surface of the fifth upper pharyngeal tooth plate of most characiforms is typically relatively flat and dentigerous (e.g., Brycon falcatus, Figure 17, and Xenocharax spilurus, Figure 4). That tooth plate extends posteriorly a limited horizontal distance, from the posterior limit of the fourth upper pharyngeal tooth plate (UP_4) to the middle of the horizontal extent of the fourth epibranchial. The broad range in the form of the fifth upper pharyngeal tooth plate (UP_5) within the Curimatidae serves to define a number of subassemblages of the family. All members of the Curimatidae have the amount of dentition on the fifth upper pharyngeal tooth plate reduced, even in juveniles, relative to the condition in outgroups (Figures 5, 7–11), a derived feature (SYNAPOMORPHY 5). Both the fifth upper pharyngeal tooth plate and the associated dentition undergo further modifications within the family.

The shortest and least elaborate version of UP_5 occurs in the species of Curimatopsis. The tooth plate in that genus has a distinct patch of teeth on its ventral surface and a short dorsomedial shaft posteriorly (Figures 5, 15). The overall longitudinal dimension of UP_5 relative to E_4 is only somewhat longer than the state of that element typical of prochilodontids (e.g., Prochilodus nigricans, Figure 16) and examined characiform outgroups (e.g., Brycon falcatus, Figure 17). In the species of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella and Cyphocharax the fifth upper pharyngeal tooth plate is more elongate longitudinally (Figures 7–11) with the relatively short posterior shaft of the element characteristic of Curimatopsis lengthened to various degrees. The shape of the lengthened posterior portion of UP_5 mirrors the form of the region of the fifth ceratobranchial which it approximates when the dorsal and ventral portions of the gill arches are in contact. Although a number of genera of non-Curimatopsis curimatids have a variable number of teeth on the ventral surface of the fifth upper pharyngeal tooth plate as juveniles (Figure 7), the adults of those taxa are characterized by a pronounced reduction, or more typically an elimination of the dentition associated with UP_5. On the basis of outgroup comparisons both the increase in the relative length of UP_5, and the decrease in the amount of dentition on that tooth plate are hypothesized to be shared derived characters uniting Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 54).

FIGURE 14.—Curimata cyprinoides, USNM 225619, dorsal portion of gill arches, left side, ventral view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 15.—Curimatopsis microlepis, MZUSP 21053, dorsal portion of gill arches, left side, ventral view, anterior to left (dense patterned stippling represents cartilage).

The apomorphous elongate form of UP_5 typical for non-Curimatopsis curimatids is further modified in various ways in some less inclusive subunits of the Curimatidae. Only one of these modifications is, however, derived for a group herein recognized at the generic level and thus appropriate for this discussion. Species of the genus Psectrogaster have an extremely elongate fifth upper pharyngeal tooth plate which extends caudally beyond the transverse plane through the posterior limit of the ossified portions of the gill arches (Figure 9). Such a posterior extension of the bone in Psectrogaster contrasts with the typical curimatid condition in which the fifth upper pharyngeal tooth plate barely reaches, or more usually falls distinctly short of, that transverse plane. The distal portion of UP_5 of species of Psectrogaster is also twisted along its longitudinal axis, and is transversely expanded distally into an oar-shaped process; an apomorphous restructuring of the element again unknown elsewhere in the family. In light of the unique nature of the lengthening of UP_5 and its reconfiguration, the overall form of the bone is considered a derived character synapomorphous for the species of Psectrogaster (SYNAPOMORPHY 87).

Fourth Upper Pharyngeal Tooth Plate (UP[4]) and Fourth Infrapharyngobranchial (PB[4])

In both the Curimatidae (Figure 15) and Prochilodontidae (Figure 16) an edentulous ossification envelopes most of the ventral surface and portions of the lateral margins of the cartilaginous fourth infrapharyngobranchial (PB_4). The homology of this ossification is somewhat problematical. It may represent a new perichondral element, with the fourth upper pharyngeal tooth plate (UP_4) usually attached to the ventral surface of the fourth infrapharyngobranchial being absent. Alternatively, the ossification along the ventral and lateral surfaces of PB_4 in the Curimatidae and Prochilodontidae may represent a restructured edentulous fourth upper pharyngeal tooth plate. The latter homology is tentatively proposed since it requires only one ad hoc hypothesis, the modification in the overall structure of UP_4. The alternative hypothesis, that the ossification represents a new perichondral element, necessitates two assumptions, the loss of UP_4 and the independent development of a new ossification on PB_4, a more complex scenario. A more definitive statement on the homology of the ossification on the ventral portion of PB_4 would necessitate presently unavailable ontogenetic information.

FIGURE 16.—Prochilodus nigricans, USNM 231438, dorsal portion of gill arches, left side, ventral view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 17.—Brycon falcatus, USNM 226161, dorsal portion of gill arches, left side, ventral view, anterior to left (dense patterned stippling represents cartilage).

A definitive statement on the homology of the element is not crucial in terms of its phylogenetic significance. If the ossification is the fourth upper pharyngeal tooth plate it would, as was noted by Vari (1983:18), represent a pronounced restructuring of the plesiomorphous plate-like UP_4 (Figure 17) that typically contacts only the ventral surface of PB_4 in most characiforms. Similarly a new perichondral ossification on the ventral surface of PB_4 and the loss of UP_4 would also be derived. The expanded curved ossification on PB_4 was consequently considered derived by Vari (1983) and a synapomorphy for the Curimatidae and Prochilodontidae (SYNAPOMORPHY 4). Subsequent outgroup analysis has shown that the overall profile of the resultant UP_4-PB_4 bone-cartilage complex in those families is also phylogenetically informative. The typical, and hypothesized plesiomorphous, form of the fourth infrapharyngobranchial in characiforms has a relatively straight or moderately convex lateral margin when viewed from a ventral view. That form of PB_4 is common to the majority of characiforms including several diverse families: Citharinidae (Citharinus Cuvier); Distichodontidae (Neolebias Steindachner (Vari, 1979:305), Mesoborus Pellegrin, and Xenocharax); Characidae, including genera from the Neotropics (Agoniates Müller and Troschel, Brycon (Figure 17), Clupeacharax, Exodon Müller and Troschel, Hollandichthys Eigenmann) and the Old World (Alestes Müller and Troschel, Hydrocynus Cuvier (Brewster, 1986, fig. 14), Phenacogrammus); Chilodontidae (Caenotropus Günther (see Vari, 1983, figs. 18, 19)); Hemiodontidae (Hemiodopsis Fowler); and Parodontidae (Parodon Valenciennes). In all examined members of the Curimatidae and Prochilodontidae the anterior portion of PB_4 and the associated anterior section of UP_4 are transversely expanded laterally which results in the overlap of the anteromedial surface of the third epibranchial (E_3) by the conjoined PB_4 and UP_4. As a consequence of this anterior expansion, the PB_4-UP_4 complex appears transversely constricted midway along its longitudinal length (Figures 15, 16) contrary to the relatively parallel, or outwardly bowed lateral margin of that complex in other examined characiforms (e.g., Brycon falcatus, Figure 17). Outgroup comparisons have failed to reveal comparable modifications in other examined characiforms, and the form of the PB_4-UP_4 bone-cartilage complex is thus considered synapomorphous for the members of the Curimatidae and Prochilodontidae (SYNAPOMORPHY 12).

The form of the conjoined UP_4-PB_4 common to curimatids and prochilodontids is further modified in one generic level subunit of the Curimatidae. Potamorhina species have both the fourth infrapharyngobranchial and the associated fourth upper pharygneal tooth plate significantly lengthened longitudinally (Figure 10). That adaptation is considered derived (SYNAPOMORPHY 66) with respect to the relatively shorter form of these elements in other curimatids and the families that constitute the nested sister groups to the Curimatidae.

Third Epibranchial (E[3])

The dorsal portion of the third branchial arch consists of two bones, the third epibranchial (E_3) and third infrapharyngobranchial (PB_3) along with their associated cartilages. Derived modifications of those elements unite the Prochilodontidae and Curimatidae, and define lineages within the latter family. The apomorphous modifications of the third epibranchial will be discussed first.

The generalized form of the third epibranchial among characiforms has a cartilage capped uncinate process (UN) whose distal portion (DCE_3) terminates both distinctly lateral of the median plane of the gill arches, and posterior of the junction of the third infrapharyngobranchial with the third epibranchial and fourth infrapharyngobranchial (Figures 4, 18). All members of the Curimatidae and Prochilodontidae have the uncinate process of the third epibranchial markedly modified. In those two families the uncinate process is oriented anteriorly (Figure 19) rather than retaining the lateral or slightly anterolateral alignment found in other characiforms (Figure 18). As a consequence of this realignment the uncinate process with its associated distal cartilage overlays the vertical plane through the articulation between PB_3 and E_3 rather than terminating distinctly posterior of that articulation. The uncinate process additionally more closely approaches the median plane of the arches than is typical in characiform outgroups. Correlated with these changes is the approximation with the uncinate process to the midventral basal portion of the neurocranium to which it is attached by a ligamentous band. Together these hypothesized derived modifications are considered a synapomorphy for the Curimatidae and Prochilodontidae (SYNAPOMORPHY 13).

FIGURE 18.—Brycon falcatus, USNM 226161, fourth infrapharyngobranchial, posterior portion of third infrapharyngobranchial, and anterior portion of third epibranchial, right side, dorsal view, anterior to left (dense patterned stippling represents cartilage).

FIGURE 19.—Curimata cisandina, USNM 229171, fourth infrapharyngobranchial, fourth upper pharyngeal tooth plate, posterior portion of third infrapharyngobranchial, and third epibranchial, right side, dorsal view, anterior to left (dense patterned stippling represents cartilage).

The anterior portion of the main shaft of E_3 in characiform outgroups is capped anteriorly by a relatively large articular cartilage that contacts the lateral half of the posterior margin of the cartilaginous third infrapharyngobranchial (PB_3). Medially that cartilage cap of the third epibranchial (ASE[3], Figure 18) slightly overlies and abuts the dorsolateral surface of the fourth infrapharyngobranchial (PB_4, but is distinctly separated from the midsagittal plane. The anterior portion of the main shaft of E_3 in the Curimatidae and Prochilodontidae is significantly modified relative to that generalized bauplan. Rather than terminating as a single articular surface along the posterolateral margin of the third infrapharyngobranchial, the articular surface of the third epibranchial in the Curimatidae and Prochilodontidae is divided into two subsections. The anterolateral margin of E_3 retains contact with the cartilage along the posterolateral portion of PB_3 (LPE[3], Figure 19). In contrast, the relatively small medial extension of the anterolateral portion of the third epibrancial that characteristically extends over the dorsolateral surface of the fourth infrapharyngobranchial of most characiforms is totally altered in these two families. Curimatids and prochilodontids have the medial extension expanded into a relatively thick ossified process (MPE[3], Figure 19) which extends over the anterodorsal portion of the fourth infrapharyngobranchial and terminates medially in a relatively large cartilage cap. This medially expanded process extends along and is surrounded posteroventrally by a matching groove in the anterodorsal surface of the cartilaginous fourth infrapharyngobranchial (PB_4). As a consequence the medial process of the third epibranchial in both families is visible in a medial view of the dorsal portions of the gill arches (Figures 5, 6, 8–11). The lateral expansion and ossification of the medial process of the third epibranchial, and associated reconfiguration of the proximate portion of PB_4 in the Curimatidae and Prochilodontidae are considered derived relative to the condition of these elements in other characiforms, and together represent a synapomorphy for those families (SYNAPOMORPHY 14).

A medial elongation of the anterior portion of PB_3 also occurs among characiforms in the Anostomidae (Vari, 1983, fig. 20), Chilodontidae (Vari, 1983, fig. 19), Hemiodontidae, and Parodontidae. None of the cited families has the third epibranchial terminating anteriorly in a large medial process comparable to that of the Curimatidae and Prochilodontidae. With the exception of the Chilodontidae (Chilodus Müller and Troschel, Caenotropus) and a single genus in the Hemiodontidae (Bivibranchia Eigenmann, sensu Vari, 1985), the cartilage along the anteromedial portions of the articular surface on the third epibranchial in these families is continuous with the lateral portion of that cartilage contacting the fourth infrapharyngobranchial. Such continuity contrasts with the subdivision of that cartilage cap into two independent masses in the Curimatidae and Prochilodontidae. As noted, the Chilodontidae has two distinct distal cartilages on the anterior portion of E_3 (e.g., Caenotropus, Vari, 1983, fig. 19). The medial section of that portion of the bone, however, consists of a slender shaft approximating but not reaching the medial plane, a significantly different condition than that found in the Curimatidae and Prochilodontidae.

Furthermore the Chilodontidae shares numerous synapomorphies with, and is evidently most closely related to the Anostomidae (Vari, 1983:50) which lacks comparable derived restructurings of the anterior portion of the third epibranchial. The medial process of the third epibranchial in Bivibranchia more closely approximates the form of the structure in the Curimatidae and Prochilodontidae, but differs from the condition in those families in details of its site of origin and overall morphology. Moreover, Argonectes Bòhlke and Myers, which is evidently the closest relative of Bivibranchia (Roberts, 1974), together with all the other members of the Hemiodontidae lack such a distinct medial process on E_3. The noted differences in the structure of the third epibranchial in the Curimatidae and Prochilodontidae versus those in the Chilodontidae and Bivibranchia, in conjunction with the data on phylogenetic relationships of those taxa (Vari, 1983; Roberts, 1974) make it simplest to assume that the modifications in the Chilodontidae and Bivibranchia are non-homologous with the described alterations of the third epibranchial hypothesized synapomorphous for the Curimatidae and Prochilodontidae.

All members of the Curimatidae have at least a slight ridge along the ventral surface of E_3 extending in line with the longitudinal axis of the element. This ridge is further elaborated in two subunits of the family. A well developed ridge is characteristic of all members of Psectrogaster (SYNAPOMORPHY 88). Similarly a very strong ventral ridge on E_3 is shared by a clade consisting of three nominal species within Curimata (aspera, simulata, and cerasina); an elaboration which in those species parallels the ridge on the opposing dorsal surface of the third ceratobranchial of the ventral portion of the branchial basket. The common possession of the ventral ridge in Psectrogaster and a subunit of Curimata is considered homoplasious in the overall most parsimonious scheme of relationships within the family, although synapomorphous for each of those clades (see “Synapomorphy List and Phylogenetic Reconstruction” and “Convergent Characters”).

Third Infrapharyngobranchial (PB[3])

The third infrapharyngobranchial (PB_3) is typically a flattened or slightly dorsally concave, longitudinally elongate triangular bone in characiforms. As a consequence of its flattened form the ossification lies entirely or nearly entirely in the horizontal plane through the ventral surface of the upper portions of the gill arches. The lateral portion of PB_3 is consequently not visible or only slightly visible in a medial view of that complex (e.g., Xenocharax spilurus, Figure 4). Such a flattened PB_3 characterizes the Anostomidae and Chilodontidae which together constitute the sister clade to the lineage formed by the Prochilodontidae and Curimatidae. The Prochilodontidae and Curimatidae rather than retaining the flattened PB_3 of other characiforms have the posterolateral portion of the ossification restructured into a vertically or near vertically aligned flange that extends distinctly dorsal of the horizontal plane through the ventral main portion of the ossification. This restructuring results in the lateral portion of the bone being readily visible in a median view of the gill arches in both curimatids and prochilodontids (DFPB[3], Figures 5, 6, 8–11). The unique nature of this modification of the third pharyngobranchial in those two families is indicative of the derived nature of the character and is another derived attribute supporting the hypothesis of the monophyly of the clade formed by the Curimatidae and Prochilodontidae (SYNAPOMORPHY 15).

The association of the third infrapharyngobrancial (PB_3) with its respective epibranchial (E_3) and of PB_3 with the fourth infrapharyngobranchial (PB_4) varies within the family Curimatidae. The form of PB_3 typical for characiforms has a continuous articular cartilage along its posterior margin. The medial portion of the posterior PB_3 cartilage contacts the anterior margin of the cartilaginous PB_4, and the lateral portion of that cartilage of PB_3 abuts the articular cartilage that caps the anterior section of E_3 (Figure 16, 17). In most characiforms the joint of PB_3 with PB_4 and E_3 is either transversely straight (Figure 16) or at a slight angle (Figure 17), but there is no pronounced overlap of PB_3 lateral to the ossified portion of E_3. All Curimatopsis species (Figure 15), in contrast, have the joint between the third infrapharyngobranchial and third epibranchial distinctly oblique relative to a transverse plane through the branchial basket. As a consequence of the restructuring the posterolateral portion of the third infrapharyngobranchial apomorphously extends posteriorly into the region primitively occupied by the anterolateral portion of the third epibranchial (compare Figures 15–17), a derived condition (SYNAPOMORPHY 43). The overlap between these elements found in some members of the Old World characiform family Distichodontidae (e.g., Mesoborus) is a function of the posterolateral development of a process of PB_3 that extends lateral of the anterolateral edge of the ossified portion of E_3 rather than a consequence of the realignment of the PB_3-E_3 joint, and thus is non-homologous with the condition in Curimatopsis.

As noted, it appears that a continuous cartilage cap along the posterior margin of the third infrapharygobranchial is the primitive condition of that element in characiforms. Such an articular surface is common to the Prochilodontidae (Figure 16), New and Old World members of the Characidae (e.g., Brycon, Figure 17), the Hemiodontidae, Hepsetidae, Citharinidae, Distichodontidae, and other characiform outgroups examined. Such a continuous cartilage cap on PB_3 is also characteristic of all members of Curimatopsis (Figure 15) in the Curimatidae. In the species of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax this hypothesized plesiomorphic single cartilage mass on PB_3 is subdivided sagitally (SYNAPOMORPHY 55). The medial portion of the cartilage mass of the third infrapharyngobranchial articulates with the anterior surface of the fourth infrapharygobranchial. The lateral section of the cartilage, located along the dorsal flange of the third infrapharyngobranchial (DFPB_3), contacts the anterior articular cartilage of E_3 (Figures 8, 10, 11). A distinct ossified region along the posterior border of the third infrapharyngobranchial separates these two cartilage masses.

Although hypothesized to be a derived character common to all genera other than Curimatopsis within the Curimatidae, a subdivision of the posterior articular cartilage on the third infrapharyngobranchial is not unique to that assemblage among characiforms. The transversely widened PB_3 of the Chilodontidae and Anostomidae demonstrates a similar fission of the posterior cartilage mass (see Vari, 1983, figs. 18, 19). Within the Hemiodontidae, a comparable transversely divided articular surface is limited to Bivibranchia (sensu Vari, 1985). The overall hypothesis of relationships for the Curimatidae, Prochilodontidae, Anostomidae, and Chilodontidae (Vari, 1983) indicates that the common presence of a subdivided PB_3 cartilage in the majority of the genera in the Curimatidae, and in the clade consisting of the Anostomidae and Chilodontidae may represent a homoplasious independent acquisition of that derived feature in those two lineages. An alternative hypothesis is its loss in the ancestors of the Prochilodontidae and in the lineage consisting of Curimatopsis;; or by the fusion of those cartilage bodies in the common ancestor of Curimatidae and Prochilodontidae and the subsequent fission of the cartilage in non-Curimatopsis curimatids. The hypothesis of the independent acquisition of a subdivided cartilage in the clade formedby the Anostomidae and Chilodontidae, and in non-Curimatopsis curimatids proposed in this study is more parsimonious by one step than the cited possible alternative ad hoc hypotheses. Thus, the possession of two discrete articular cartilages on the posterior of PB_3 is considered a synapomorphy for Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

The hypothesis of the independent acquisition of a subdivided PB_3 articular cartilage within and outside of the Curimatidae can also be applied from a functional basis. In the Chilodontidae and Anostomidae the subdivision of the articular cartilage is apparently correlated with the pronounced transverse widening of the third infrapharyngobranchial. Such a transverse expansion of the third infrapharyngobranchial is not found in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax that rather demonstrate a dorsal expansion of the lateral region of the bone. The common possession of a subdivided posterior articular cartilage in non-Curimatopsis curimatids and Bivibranchia is similarly considered homoplasious. Available data indicates that Bivibranchia is a highly modified member of the Hemiodontidae that is evidently most closely related to Argonectes (Roberts, 1974:432). Neither Argonectes, the presumed sister group to Bivibranchia, nor any other of the examined hemiodontid genera (Anodus, Hemiodopsis, Hemiodus Müller and Troschel, Micromischodus Roberts) have the transverse development of the medial portion of PB_3 typical of Bivibranchia, nor do they have the transverse subdivision of the posterior articular cartilage on that element that characterizes that genus. It is thus simplest to consider the presence of a subdivided PB_3 articular surface in Bivibranchia as being independently acquired and thus not homologoous to the similar modifications in non-Curimatopsis curimatids.

Second Branchial Arch

The second epibranchial (E_2) and second infrapharyngobranchial (PB_2) of characiforms typically articulate along a plane nearly transverse to the main longitudinal axis of the branchial complex. The second epibranchial ranges from rounded to somewhat V-shaped in cross section, but with its ventral margin rounded in either case. The second infrapharyngobranchial is flanked anterolaterally by the anteromedial portion of the first epibranchial, and along its medial surface contacts the lateral surface of the anterior half of the third infrapharyngobranchial. The contact between these elements is strengthened by ligamentous connections, but not via elaborations of the ossified portion of PB_2.

The complex consisting of the second epibranchial and the second infrapharyngobranchial exhibits within the Curimatidae some modifications similar to those that occur on the third branchial arch in that family. The angled area of contact noted above for the third epibranchial and third infrapharyngobranchial in Curimatopsis is paralleled and indeed carried even further on the second gill arch (Figure 15). All Curimatopsis species have a significant reduction of the anterolateral margin of the second epibranchial. The lateral margin of PB_2 in the species of that genus is, in turn, expanded laterally into the region occupied in other characiforms and curimatids by the anterolateral portion of E_2. This significantly increases the size of PB_2 and results in a unique transversely angled articulation between the second epibranchial and second infrapharyngobranchial. These conditions are together considered a snyapomorphy for the genus (SYNAPOMORPHY 44).

All species of Psectrogaster have longitudinally aligned ridges along the ventral surface of the second epibranchial comparable to those of the third epibranchial. These ridges, which contrast with the ventrally unelaborated second epibranchial generalized for characiforms, are another derived character hypothesized synapomorphous for the members of the genus (SYNAPOMORPHY 89). Similar ridges are found in a subunit of Curimata (mivartii, cerasina, aspera, simulata, alleni, cisandina, and two undescribed species). As in the case of the ridge on the third epibranchial, the most parsimonious hypothesis of relationships within the Curimatidae (see “Synapomorphy List and Phylogenetic Reconstruction” and “Convergent Characters”) indicates that the ridges in Psectrogaster and the cited subunit of Curimata represent independent acquisitions of those elaborations.

The medialmost element of the dorsal portion of the second branchial arch, the second infrapharyngobranchial (PB_2) also demonstrates various derived modifications. The posterolateral elaboration of the element associated with the expansion of the articular surface between the second infrapharyngobranchial and second epibranchial in Curimatopsis was noted above. In the species of Steindachnerina the anteromedial surface of the third infrapharyngobranchial fits into a depression on the lateral surface of the second infrapharyngobranchial (PB_2) (Figure 20). Ventrally PB_2 has an ossified shelf (VLF) extending along the ventral margin of PB_3 and dorsally there is a vertical plate (DLF) extending along the medial surface of that element. These processes are moderately developed in the nominal species and subspecies S. argentea, S. conspersa, S. bimaculata, S. trachysteta, S. bimaculata sialis, S. pterostigma, S. semiornata, S. melanira, S. leucisca leucisca, S. leucisca bolivae, and S. binotata, and more elaborately developed in the remaining members of the genus. The possession of such processes whether moderately or well developed is considered a synapomorphy for the genus (SYNAPOMORPHY 97).

FIGURE 20.—Steindachnerina hypostoma, USNM 167802, second infrapharyngobranchial, right side, posterior view, medial to left (dense patterned stippling represents cartilage).

Psectrogaster species also have a distinct flange on the dorsal surface of PB_2 (SYNAPOMORPHY 90) comparable to that in Steindachnerina, particularly those species of Steindachnerina with the more elaborate vertical development of the flange. However Psectrogaster lacks the ventral shelf overlapping the ventral surface of PB_3. Although comparable in overall form, I consider the similarly placed dorsal processes on the lateral surface of the second infraphyarngobranchial in Steindachnerina and Psectrogaster to be homoplasious within the context of the overall most parsimonious hypothesis of relationships (see “Convergent Characters”).

First Branchial Arch

The typical characiform first branchial arch has a ventrally unelaborated first epibranchial (E_1) and a moderate sized first infrapharyngobranchial (PB_1) whose cartilaginous basal section is smaller than the ossified portion which typically forms the dorsal section of that element. The dorsally located uncinate process of the first epibranchial extends from the anteromedial surface of E_1, having the form of a discrete process terminating anteriorly in a cartilaginous body that contacts a corresponding cartilage on the dorsal surface of the uncinate process of the second infrapharyngobranchial (PB_2).

Both of the elements of the first branchial arch, the first infrapharyngobranchial and first epibranchial, demonstrate apomorphous modifications within the Curimatidae. In all members of Curimata, PB_1 is either proportionally reduced in size compared to the moderate sized PB_1 typical of most characiforms, or is completely lacking. This progressive reduction and loss of the first infrapharyngobranchial is hypothesized as derived given the condition in the outgroups, and is thus a synapomorphy for the species of Curimata (SYNAPOMORPHY 81). Steindachnerina species do not demonstrate any marked changes in the ossified portion of the first infrapharyngobranchial, but the medial cartilaginous section of the element is greatly enlarged, being more extensive than the ossified portion of the first infrapharyngobranchial and contacting the anterior portions of both the first epibranchial and second infrapharyngobranchial. This condition represents an evidently derived state relative to the morphology of those components common to other curimatids in which the ossified portion of the first infrapharyngobranchial is the larger, and wherein the first and second infrapharyngobranchials are typically not in contact (SYNAPOMORPHY 98).

The typical first epibranchial in characiforms is V-shaped in cross section and most commonly unelaborated on its ventral surface. A well-developed ridge on the ventral surface of E_1 is typical for the species of Psectrogaster, a hypothesized derived condition given the absence of such an elaboration in characiform outgroups (SYNAPOMORPHY 91). A longitudinal ridge is also present ventrally on the E_1 of Curimata species, but ranges within that genus in its degree of development. The well-developed ridge comparable to that of Psectrogaster occurs only in two species of Curimata and the overall most parsimonious hypothesis of relationships within the Curimatidae indicates that the presence of such a ridge in Curimata is non-homologous with the ridge characteristic of Psectrogaster species (see “Synapomorphy List and Phylogenetic Reconstruction” and “Convergent Characters”).

Outgroup studies indicate that the first epibranchial in characiforms has a small to moderate sized, dorsally located uncinate process that terminates in a single cartilaginous cap which contacts a corresponding articular cartilage on the dorsal surface of the second infrapharyngobranchial. Potamorhina species, in contrast, have a well developed E_1 uncinate process which has two distinct subsections distally, each terminating in a distal cartilage cap (UN, Figure 21) (SYNAPOMORPHY 71). The anterior of the two articular surface contacts the matching cartilage body on the uncinate process that arises from the anteroventral portion of PB_2. The posterior cartilage-capped articular surface of the uncinate process of E_1 extends dorsally from the main body of the process at an angle of approximately 45° relative to its partner and approximates the neurocranium dorsally. Two separate articular surfaces on the uncinate process of E_1 also occur in all nominal species of Curimata other than C. ocellata, C. semitaeniata, C. vittata, C. murieli, and C. macrops. The subdivided cartilage cap on the E_1 uncinate process of most Curimata species differs, however, from the state in Potamorhina in its overall morphology and details of its spatial relationships with the second infrapharyngobranchial. Within Curimata it is also possible to follow the ontogenetic and phylogenetic expansion of the distal portion of the uncinate process of E_1, and the fission of its articular surface into two subunits. No internal evidence of such a subdivision exists for the species for Potamorhina, and it is possible that the situation in that genus does not represent a subdivision of the original cartilaginous articular surface, but rather the de novo development of a second cartilage body on the uncinate process. Furthermore, the overall hypothesis of relationships within the Curimatidae indicates that these two cartilage-capped surfaces on the E_1 uncinate process in Potamorhina and a subunit of Curimata are independently achieved (see “Synapomorphy List and Phylogenetic Reconstruction”).

FIGURE 21.—Potamorhina squamoralevis, USNM 243228, first epibranchial, right side, anterior portion, posterior view, median plane to right (dense patterned stippling represents cartilage).

Ventral Portion of Branchial Arches

Although not demonstrating such dramatic derived restructurings as are found in the dorsal portions of the gill arches, the ventral elements of the branchial basket have a number of modifications pertinent to the question of the monophyly of the Curimatidae and relative to the relationships of its constituent genera. In the following discussion, the analysis is arranged around subunits of the arches that typically consist of individual elements.

First Basibranchial (BB[1])

The generalized condition for characiforms is the possession of a distinct, typically rod-shaped, medial first basibranchial situated posterior of the basihyal and anterior of the second basibranchial. As noted by Vari (1983:14) prochilodontids have a small triangular first basibranchial that abuts the anterior margin of the second basibranchial and which barely extends to the level of the first hypobranchial (see Vari, 1983, fig. 9). A recognizable first basibranchial is, in turn, lacking in all curimatids (Figure 25). This reductive trend is hypothesized to be apomorphous at two levels of universality. The reduction of the first basibranchial or the absence of that element as a discrete ossification are together considered a synapomorphy for the Prochilodontidae and Curimatidae (SYNAPOMORPHY 6). The absence of an ossified first basibranchial is, in turn, considered a synapomorphy for the members of the family (SYNAPOMORPHY 19) (see Vari, 1983:14 for a further discussion of this complex).

Second Hypobranchial (H[2])

The articular cartilaginous surface of the second hypobranchial of most characiforms consists of two subunits, a smaller cartilage body at the anterolateral corner of the ossification and an extensive cartilage along the medial and posterior portions of the bone (Figure 22A). This morphology is found in the Anostomidae, Chilodontidae, and Prochilodontidae, and among curimatids also occurs in the genus Curimatopsis. Potamorhina species retain two separate cartilages anteriorly, but the separation between them is considerably reduced (Figure 22B). The genera Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax have a continuous cartilage body extending along the anterior and at least part of the medial surface of the element (Figure 22C) rather than two separate cartilages. In light of the broad separation anteriorly of the cartilages on the second hypobranchial in characiform outgroups, the reduction or elimination of the gap between the two anterior cartilages is considered a synapomorphy for the members of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Curimatella, and Cyphocharax (SYNAPOMORPHY 56). The fusion of the two anterior cartilages into a continuous body in Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is, in turn, hypothesized to be a synapomorphy for those taxa (SYNAPOMORPHY 75) (see also discussion immediately following).

FIGURE 22.—Second hypobranchial: A, Curimatopsis microlepis, USNM 268867; B, Potamorhina laticeps, USNM 121325; C, Psectrogaster amazonica, USNM 261518; and D, Pseudocurimata peruana, USNM 285667. (Right side, dorsal view, anterior at top, lateral to left, dense patterned stippling represents cartilage.)

The continuous cartilage along the anterior border and anterior two-thirds of the medial margin of the second hypobranchial in that clade undergoes a secondary fission in the species of Pseudocurimata. In those taxa both the ossified and cartilaginous portions of the second hypobranchial proximate to the anterolateral margin of the third basibranchial are expanded vertically to form a more extensive articular surface (Figure 22D). Associated with that expansion is the separation of the continuous articular cartilage characteristic of proximate sister groups of Pseudocurimata into a broad anterior section and an elongate medial portion, with the two cartilages separated by an ossified region at the anteromedial angle of the bone. The expansion of the medial portion of the second hypobranchial and the subdivision of the originally continuous cartilage body along its anterior and medial margins are together considered a synapomorphy for the species of Pseudocurimata (SYNAPOMORPHY 101).

As noted above, a subdivided cartilage along the anterior and medial margins of the second hypobranchial also occurs in Curimatopsis and Potamorhina, in which that condition was hypothesized to be plesiomorphous. The forms of the cartilages on this element in Curimatopsis and Potamorhina on the one hand and Pseudocurimata on the other differ both in their relative locations and overall forms. The anterior cartilage in Curimatopsis and particularly Potamorhina is a small conical body limited to a process on the anterolateral corner of the bone. The anterior cartilage of Pseudocurimata, in contrast, is a narrow body extending over a broad portion of that margin of the bone. Similarly the gaps between the two cartilages are located in different regions in the two genera (compare Figure 22A,B with 22D). Futhermore the thickening characteristic of the second hypobranchial in Pseudocurimata species is absent in Curimatopsis. These morphological differences lead to a hypothesis of the non-homology of the two cartilage bodies on the anterior and medial margins of the second hypobranchial in Curimatopsis and Potamorhina versus Pseudocurimata, a hypothesis congruent with the overall most parsimonious scheme of relationships within the family (Figure 44).

Third Hypobranchial (H[3])

The third hypobranchial in characiforms is typically a flattened ossification that is unelaborated ventrally. The bone slants anteroventrally lateral to the third basibranchial, and terminates anteriorly in a rounded to distinctly acute triangular point. The anterior terminus of the third hypobranchial, be it an oblique point or an acute angle, serves as the point of attachment for a ligament that extends to the posteromedial surface of the second hypobranchial. The just described hypothesized plesiomorphous condition of the third hypobranchial is notably modified in all species of the Curimatidae. The members of the family have the anteroventral portion of the third hypobranchial elaborated into a discrete ventral process bearing both anterior and posterior extensions (AE and PE; Figures 23, 24). These elaborations, which lie in the connective tissue complex which parallels the walls of the ventral aorta, are not typical for characiforms and are hypothesized to be synapomorphous for the members of the Curimatidae (SYNAPOMORPHY 18).

Members of the family Hemiodontidae (Anodus, Hemiodus, Hemiodopsis (Vari, 1982a:19), Micromischodus, Bivibranchia [including Atomaster, Vari, 1985:512], and Argonectes) and one genus in the Chilodontidae (Caenotropus labyrinthicus) have the anterior portion of H_3 more developed ventrally than is the case in most characiforms. As a consequence the overall morphology of the anterior section of H_3 in those taxa is somewhat reminiscent of the anterior portion of the ventral H_3 complex of curimatids. Furthermore, two of the taxa, Anodus and Caenotropus labyrinthicus, also have the vertical flanges on the ventral surface of the third hypobranchial expanded in the connective tissue next to the walls of the ventral aorta, conditions similar to those characteristic of curimatids. The ventral elaborations and flanges in these genera differ from the similar processes in curimatids in a number of attributes. The ligament connecting the second and third hypobranchials in the Hemiodontidae and Caenotropus arises from the anterior tip of the anterior process of the third hypobranchial. That association of the ligament with that portion of the process is congruent with the hypothesis that the point of attachment, the elongate anterior point, in those taxa carried the H_2-H_3 ligament forward with it during its phylogenetic expansion anteriorly. Thus the lengthened anterior process of hemiodontids and Caenotropus is a consequence of the greater development of the entire ventral section of the third hypobranchial. In the Curimatidae, in contrast, the ligament attaches to the dorsal surface of the ventral process of the third hypobranchial proximate to the main body of that element (IL, Figures 23 and 24). The anterior projection of the ventral process, in turn, extends anteriorly distinctly ventral of the point of attachment of the ligament on the third hypobranchial. Thus it appears that the elongate anterior portion of the bone in the Curimatidae represents an anterior outgrowth of that portion of the bone ventral of the point of attachment of the ligament rather than an elongation of the entire element as is the case in the Hemiodontidae and Caenotropus.

FIGURE 23.—Curimata cyprinoides, USNM 267964, third basibranchial, third hypobranchial, and anterior portion of third ceratobranchials, ventral view, anterior at top (dense patterned stippling represents cartilage).

The cited hemiodontids and chilodontids also differ from curimatids in the absence of any posterior extension on the ventral processes of H_3. Those differences in the details of the ventral process of H_3 and the overall most parsimonious hypothesis of phylogenetic relationships of the Curimatidae to characiform outgroups (Vari, 1983) lead to a hypothesis that the restructuring of the ventral surface of the third hypobranchial in the Curimatidae is a synapomorphy for that family, achieved in a different fashion in the Hemiodontidae and one genus in the Chilodontidae.

FIGURE 24.—Steindachnerina hypostoma, USNM 167802, third basibranchial and third hypobranchial, right side, lateral view, anterior to right (dense patterned stippling represents cartilage).

The area of attachment on the third hypobranchial for the ligament that extends between that element and the second hypobranchial (H_2) is modified in all Steindachnerina species. The connective tissue band between H_2 and H_3 typically attaches to the unelaborated anterolateral surface of the vertical strut of the ventral process of the third hypobranchial, or attaches to a slightly developed process in that area. In Steindachnerina species the point of attachment of the ligament on H_3 is rather a distinct process on the anterolateral surface of the ventral process. This condition is hypothesized to be derived given the absence of such a process in examined characiform outgroups and other lineages in the Curimatidae (IL, Figure 24) (SYNAPOMORPHY 99).

Third Ceratobranchial (C[3])

The third ceratobranchial of outgroups to the Curimatidae, including the Prochilodontidae has its dorsal margin transversely rounded or bearing a slight middorsal ridge extending along the longitudinal axis of the bone. A discrete longitudinal ridge along the dorsal surface of the bone characterizes all Psectrogaster species (SYNAPOMORPHY 92). Within Curimata a comparable ridge along the dorsal surface of C_3 also occurs in various nominal species (mivartii, aspera, simulata, cerasina, alleni, and two undescribed species) but differs in its shorter longitudinal extent along the bone. The ridge in those Curimata species also has a distinctly convex dorsal margin which contrasts with the straight edge of the ridge in Psectrogaster. The presence of a ridge, the derived condition, is considered to have arisen independently in Psectrogaster and some Curimata species within the context of the overall intrafamilial phylogeny arrived at in this study, and in light of the cited morphological differences.

Fourth Basibranchial (BB[4])

The fourth basibranchial in curimatids is a laterally compressed cartilaginous body without any associated toothplate along its dorsal surface. Only one modification of that element is pertinent to the current hypothesis of generic level relationships within the Curimatidae. In Potamorhina the gill arches are relatively elongate, an overall reconfiguration that is particularly produced in the fourth basibranchial. In all members of Potamorhina the fourth basibranchial occupies approximately two-thirds of the longitudinal extent of the branchial basket (Figure 25), an apomorphous lengthening over the condition in other curimatids and a synapomorphy for the genus (SYNAPOMORPHY 66) (see also Vari, 1984a:5 for a discussion of this character).

FIGURE 25.—Potamorhina squamoralevis, USNM 243228, ventral portion of gill arches, dorsal view, anterior at top (dense patterned stippling represents cartilage).

Fourth Ceratobranchial (C[4])

Outgroup comparisons reveal that the typical characiform fourth ceratobranchial although convex in cross section is unelaborated on its upper surface. All curimatids have various elaborations of the dorsal surface of the element relative to the hypothesized simple primitive condition. The species of Curimatopsis species have two distinct ridges running along the dorsomedial and dorsolateral margins of the bone (MR and LR, Figure 26A). These ridges extend from the wider anterior portion of the bone posteriorly along the main shaft of C_4, diverging somewhat posteriorly and are separated by a distinct longitudinal trough. The genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax, in contrast, have the ridges on the dorsal surface of the fourth ceratobranchial diverging to some degree anteriorly rather than being parallel in that region (Figure 26B,C). The ridges in those taxa are also positioned more towards the medial and lateral margins of the bone than in Curimatopsis (compare Figure 26A with 26B,C). The anterior ridge in these genera is furthermore more horizontally aligned than in Curimatopsis, a shift which results in a discrete bony pocket along the posteromedial surface of the bone. The lateral ridge in non-Curimatopsis curimatids, in turn, is rotated somewhat (Figure 26B) to distinctly lateral (Figure 26C). The presence of the ridges in one of these configurations, a character complex not present in examined characiform outgroups, is considered a synapomorphy for the species of the Curimatidae (SYNAPOMORPHY 28).

It is not possible to determine whether the parallel nearly vertical ridges along the dorsal surface of the fourth ceratobranchial, of Curimatopsis are derived, or whether the divergent, more horizontal processes characteristic of the other genera of the family are rather apomorphous. The unique nature of these processes in the Curimatidae among examined characiforms renders outgroup information useless in polarizing the transition series between the different states. Available ontogenetic data is similarly uninformative as to which state is derived. Finally the phyletic distribution of the two character states within the arrived at phylogeny is such that both the hypothesis that the Curimatopsis condition is derived and the alternative hypothesis that the ridge morphology in that genus is primitive are congruent with the final proposed scheme of relationships.

FIGURE 26.—Fourth ceratobranchial (C_4): A, Curimatopsis microlepis, USNM 268867; B, Psectrogaster ciliata, USNM 269990; C, Curimata cyprinoides, USNM 267964. (Right side, dorsal view, anterior at top, lateral to right, dense patterned stippling represents cartilage.)

The ventral portion of the fourth ceratobranchial also demonstrates some phylogenetically significant variation within the Curimatidae. That portion of the bone is unelaborated in most characiform outgroups. In the Curimatidae and Prochilodontidae, in contrast, there is a distinct process arising from the medial margin of the ventral surface of the element, an elaboration which serves as the point of attachment for various connective tissue bands (Vari, 1983:13) (SYNAPOMORPHY 8). The degree of development of this process varies drastically within the Curimatidae. Some taxa (Curimatopsis, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax) have small to very small processes on the ventral surface of the fourth ceratobranchial, whereas the genera Potamorhina, Curimata, and Psectrogaster have large, distinctly anteriorly directed processes on that element. The distribution of the enlarged processes, the presence of which is considered derived in light of the smaller processes in the Prochilodontidae and in other genera of the Curimatidae, is incongruent with the present phylogeny. Within the context of the phylogeny proposed herein (see “Synapomorphy List and Phylogenetic Reconstruction”) it is most parsimonious to consider the acquisition of an enlarged process on the fourth ceratobranchial a synapomorphy for the clade formed by all curimatids other than Curimatopsis (SYNAPOMORPHY 57), with the absence of an enlarged process in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax considered an apomorphous secondary loss (SYNAPOMORPHY 93). The alternative and next simplest hypothesis of the independent gain of an enlarged process in each of Potamorhina, Curimata, and Psectrogaster involves three ad hoc hypotheses.

Fifth Ceratobranchial (C[5])

The fifth ceratobranchial of most characiforms has a lateral shaft that terminates anteriorly in a cartilage-capped process lying proximate to the fourth basibranchial. Posteriorly that shaft ends in a cartilage at the posterolateral corner of the bone. Along the medial surface of that strut is a flattened plate that typically has a patch of small conical teeth on its dorsal surface. Such a form of C_5 is common to a variety of members of the New and Old World Characidae (e.g., Brycon, Weitzman, 1962, fig. 11), the Hemiodontidae (Roberts, 1974, fig. 32), Lebiasinidae (Weitzman, 1964, fig. 8), Erythrinidae (Roberts, 1969, fig. 35), Hepsetidae (Roberts, 1969, fig. 33), and other characiforms. As noted by Vari (1983:13), the fifth ceratobranchial of the Curimatidae and Prochilodontidae is distinctive in the significant degree of reduction or total absence of dentition on the dorsal surface of the ossification (SYNAPOMORPHY 7).

Although prochilodontids lack pharyngeal teeth on the ventral portions of the gill arches, they nonetheless retain the overall form of the fifth ceratobranchial generalized for characiforms that was just described (Figure 27A). All lineages in the Curimatidae differ from the phylogenetically widespread type of fifth ceratobranchial found in the Prochilodontidae in several respects. Members of the Curimatidae have a dorsally convex medial portion surface of the fifth ceratobranchial contrary to the flattened, although lateroventrally slanted form of the bone in examined outgroups (SYNAPOMORPHY 29). An additional derived character is the overall transverse expansion of the fifth ceratobranchial. That expansion has two components, firstly the widening of the bone medial to the portion of the bone delimited by the line extending between the anterior and posterolateral cartilage caps on the element, and secondly the further development of the ossification lateral to that line (Figure 27B,C). The transverse expansion of the fifth ceratobranchial is an additional synapomorphy for the members of the Curimatidae (SYNAPOMORPHY 30).

BUCCOPHARYNGEAL COMPLEX

The fleshy lining of the buccopharyngeal region in characiforms typically consists of a relatively smooth soft tissue layer conforming to the underlying convex inner surface of the oral cavity. Such a form of the roof of the mouth is characteristic of the Prochilodontidae and within the Curimatidae is also found in the species of Curimatopsis and Potamorhina. The genera Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax have the soft tissue layers of the buccopharyngeal region elaborated to various degrees (SYNAPOMORPHY 76). Collectively these modifications, irrespective of degree of development, are referred to herein as the buccopharyngeal complex.

The simplest form of the elaboration consists of three longitudinally oriented folds on the roof of the mouth: a median fold and a pair of lateral folds. These soft tissue folds begin somewhat behind the oral valve and terminate distinctly anterior of the dorsal portions of the gill arches. Such a relatively simple morphological plan, characteristic of the majority of curimatids, is dramatically elaborated in two subunits of the family, the genus Curimata and the majority of species in Steindachnerina.

FIGURE 27.—Fifth ceratobranchial (C_5): A, Prochilodus rubrotaeniatus, USNM 225419; B, Curimatopsis microlepis, USNM 268867;, and C, Curimata cyprinoides, USNM 267964. (Right side, dorsal view, anterior at top, lateral to right, dense patterned stippling represents cartilage.)

All Curimata species have the three primary mouth folds (MF and paired LF, Figure 28) typical of many curimatids expanded into large dangling flaps that extend ventrally from the roof of the oral cavity. These flaps abut against the oral valve anteriorly and extend posteriorly midway to the anterior terminus of the dorsal portions of the gill arches (GA). An additional innovative feature of the buccopharyngeal complex in Curimata species is the series of secondary folds (SF) on the roof of the oral cavity. These secondary folds either arise from the margins of the primary folds, or if independent of those major flaps, are aligned parallel to them. The greater degree of development of the median and lateral folds and the occurrence of secondary folds in the Curimata buccopharyngeal complex are considered derived in light of their unique nature within examined characiforms and synapomorphous for the genus (SYNAPOMORPHY 82).

The second significant elaboration of the soft tissues of the roof of the mouth within the Curimatidae involves the lobulate form of the buccopharyngeal complex characteristic of most species in Steindachnerina. All nominal members of the genus, except S. bimaculata, S. semiornata, S. trachysteta, S. bimaculata sialis, S. pterostrigma, S. melanira, S. conspersa, S. leucisca leucisca, S. leucisca bolivae, S. argentea, and S. binotata, have numerous lobulate protruberances extending ventrally from the roof of the mouth (ALP, Figure 29). These processes, which totally fill the entire anterior portion of the roof of the oral cavity, undergo an ontogenetic elaboration from relatively simple, discrete finger-like projections, to well developed, thickly packed lobulate structures. The Steindachnerina species with such complex protruberances also have in common elaborate lobed pads (PLP) to each side of the rear of the buccal cavity in the region between the rear of the anterior lobulate processes and the forward limit of the dorsal portion of the gill arches (GA, Figure 29). Those structures are not developed to a comparable degree in species of Curimata or in curimatids with less elaborate forms of the anterior portion of the buccopharyngeal complex.

FIGURE 28.—Roof of the buccopharyngeal chamber and anterior portion of gill arches of Curimata cyprinoides, USNM 267963, ventral view showing buccopharyngeal complex (hyoid apparatus, ventral portion of gill arches, eyes, and associated tissues removed).

FIGURE 29.—Roof of the buccopharyngeal chamber and anterior portion of gill arches of Steindachnerina hypostoma, USNM 261493, ventral view showing buccopharyngeal complex (hyoid apparatus, ventral portion of gill arches, eyes, and associated tissues removed).

The dangling lobulate processes in most Steindachnerina species differ significantly in position and detail from the longitudinal folds characteristic of Curimata. The hypothesis of homoplasy predicated on the basis of these morphological differences is also congruent with the most parsimonious hypothesis of relationships within the Curimatidae. That phylogenetic scheme indicates that Curimata and the subunit of Steindachnerina with buccopharyngeal complex elaborations do not constitute a monophyletic lineage, and that the increased development of the complex in the two lineages was consequently achieved independently.

The various types of buccopharyngeal complex, be they the simple three folds of many curimatid species or the more developed modifications just described for Curimata and most Steindachnerina species, all serve to increase the surface area of the dorsal surface of the buccal cavity. The buccal region of teleosts is well endowed with mucus-secreting cells (see Kapoor and Evans, 1975) and histological examinations of the foldings and lobulate bodies in curimatids with well developed buccopharyngeal complexes shows that the surfaces of these processes are profusely endowed with mucus-secreting cells (MPL, Figures 30, 31). Thus the majority of curimatids, in particular the species of Curimata and most species of Steindachnerina, presumably have a pronounced increase in their ability to generate mucus in the buccal cavity, an adaptation perhaps correlated with their specialized microphagous and detritivorous diet.

The more elaborate forms of the buccopharyngeal complex in curimatids are similar to the vomero-palatine organs of some groups of Old World cyprinids recently discussed by Reid (1982). Although Old World cyprinids and curimatids are not closely related, they do have in common a microphagous feeding habit. Reid, refining and further developing a concept suggested by Matthes (1963), hypothesized that the vomero-palatine organ in Old World cyprinids functioned in bolusformation. He proposed that the buccopharyngeal modifications served in the production of relatively large amounts of mucus, and in the mixing of such precipitating mucus with ingested particles, particularly aufwuchs (a conglomerate of algae, minute animals, detritus and inorganic matter). Field observations have shown that curimatids pick at the aufwuchs which coats many subaquatic surfaces in Neotropical freshwaters, both running and still (pers. observ.). The utilization of that food source by at least some curimatids is also indicated by the food item studies of various authors (Azevedo et al., 1938; de Godoy, 1975; Nomura and Hayashi, 1980; Nomura and Taveira, 1979). Thus Reid's hypothesis of a particle-precipitating mucus system in some Old World Ostariophysan groups is apparently also applicable to the Curimatidae, paralleling the system used by some microphytophagous cichlid fishes (Moriarty et al., 1973) and some anuran tadpoles (Wasserzug, 1972).

FIGURE 30.—Histological section through flaps of buccopharyngeal complex of Curimata cyprinoides, USNM 267963.

FIGURE 31.—Histological section through lobes of buccopharyngeal complex of Steindachnerina hypostoma, USNM 261513.

HYOID ARCH

Urohyal

The four branchiostegal rays of each side of the head in conjunction with their associated musculature and branchiostegal membranes are an interconnected complex that forms the ventral limits of the buccal cavity. In many, if not most, characiforms the branchiostegal rays and associated soft parts of each side of the head form a flexible complex that is separate (sensu McAllister, 1968) from its counterpart of the opposite side. The degree of separation of the complexes of each side varies among taxa in the order, but in many groups, particularly those with predatory or omnivorous habits, the opening extends far anteriorly resulting in an elongate gill aperture on each side. The condition in the Curimatidae differs from that generalized bauplan in having a broad connection of the branchiostegal rays of each side across the ventral midline to the contralateral complex, and with an attachment of the rays medially to the urohyal. These interconnections result in a dramatic decrease in the relative size of the aperture of the gill openings on each side of the head, and in the degree of mobility in the entire branchiostegal complex.

A broad contact between the branchiostegal ray complexes of each side comparable to that in the Curimatidae is also found in the families Prochilodontidae, Anostomidae, and Chilodontidae, which are the closest relatives of the Curimatidae. Such an extensive attachment of the complex also occurs in some characiform outgroups including the Neotropical Parodontidae and subunits of the Old World family Distichodontidae. The alterations of the hyohyoidei abductores muscles associated with the broad contact of the branchiostegal complexes of each side of the head to each other and to the urohyal, and the apomorphous nature of those modifications in the Curimatidae, Prochilodontidae, Anostomidae, and Chilodontidae were discussed by Vari (1983:45–46, fig. 40). Within that set of four families the form of the interconnection between the branchiostegals and urohyal in the species of the Curimatidae is unique in the presence of a distinctive highly developed midventral ligament (Figure 32). That ligament (MVL) is enclosed within the connective tissue complex joining the medial branchiostegal rays (BR) of the two sides and consists of a central cord-like section with anterior and posterior medially divided segments. The anterior branch of the ligament of each side is rounded in cross-section and arises from a relatively broad area on the ventral surface of the ventral hypohyal (VH). Posteriorly the central cord-like ligament subdivides into lateral band-like portions that extend along the posterior margins of the branchiostegal rays and progressively becomes thinner posteriorly. Although the medial ligamentous complex is also found in the families Chilodontidae, Anostomidae, and Prochilodontidae, it is much less well defined and not as well developed as the condition in the Curimatidae. Thus the condition in the last family is considered derived.

The central median cord-like portion of the described ligamentous complex extends along a distinct groove located along the ventromedial surface of the urohyal. That urohyal groove is delimited by ventrolaterally aligned flanges extending from the lower margin of the main body of that ossification. The Prochilodontidae, the sister group to the Curimatidae, and the Anostomidae and Chilodontidae, which together form the sister group to the curimatid-prochilodontid clade, both have the ventral portions of the urohyal expanded laterally to differing degrees; however, in all these families the bone is ventrally flattened, rather than having a central groove. Furthermore the lateral flanges in those proximate outgroups are not ventrolaterally oriented. Thus neither the highly developed ligamentous system along the midline of the branchiostegal complexes, nor the groove on the ventral surface of the urohyal are known to occur in characiforms outside of the Curimatidae. The complex formed by the midventral ligament and the urohyal is consequently hypothesized to be a synapomorphy for the members of the Curimatidae (SYNAPOMORPHY 31).

The form of the urohyal is quite variable within the Curimatidae, both in terms of overall morphology and in various details. The continuum between most different morphological states makes it difficult, if not impossible, to non-arbitrarily delimit much of that variability in terms of discrete characters applicable to a phylogenetic analysis. Several distinct character states exist which are, however, useful in generating a hypothesis of generic level relationships.

FIGURE 32.—Cyphocharax abramoides, USNM 267953, hyoid arch, anterior portion of branchiostegal rays and midventral ligament (medial portion and right side, ventral view, anterior at top, basihyal not illustrated, halves of arch separated laterally from normal positions).

As noted above, the urohyal of the Curimatidae is characterized by a posteroventrally angled flange along both sides of its ventral margin. In cross section the bone consequently has the form of an inverted “Y”; the ventral arms of which vary in the degree of lateral development within the family. In Curimatopsis the ventrolateral flanges are quite narrow along their entire length, whereas in the other lineages of the Curimatidae, the flanges are wider, sometimes considerably so, particularly anteriorly. Outgroup comparisons reveal wide flanges on the urohyal in the Prochilodontidae, the sister group to the Curimatidae. The sister clade to the lineage formed by those two families shows two divergent conditions; narrow flanges in the Anostomidae and wide processes in the Chilodontidae. The condition in the immediate outgroup, the Prochilodontidae, together with parsimony considerations in the broader outgroup, including the Anostomidae and Chilodontidae, support the hypothesis that a urohyal with wide ventrolateral flanges is primitive for the family Curimatidae. Thus the narrow processes in the species of Curimatopsis is considered a reductive feature that is synapomorphous for the members of that genus (SYNAPOMORPHY 45).

The urohyal in the Prochilodontidae, Anostomidae, and Chilodontidae are all relatively short longitudinally with their ventral portions terminating approximately at the point where the medialmost branchiostegal rays diverge laterally. The Curimatidae, in contrast, has the ventral portions of the urohyal extending moderately to distinctly beyond that point, a condition that is thus considered a synapomorphy for the members of the family (SYNAPOMORPHY 32).

Within the Curimatidae, the genera Curimatopsis, Potamorhina, and Psectrogaster all have a urohyal that is distinctly elongate, with one-third to one-half of the ossification extending beyond the rear of the point of the lateral divergence of the medial branchiostegal rays. Such a degree of posterior development of the urohyal is not found in the remainder of the family, and is considered derived on the basis of outgroup comparisons. The possession of an elongate urohyal does not, however, delimit a monophyletic subunit of the family in the final proposed intrafamilial phylogeny. Within that phyletic scheme (Figure 44), Curimatopsis and Potamorhina are sequential clades but are separated from Psectrogaster by the lineage consisting of Curimata. The sister group to Psectrogaster, the assemblage consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is characterized by short urohyals. Three equally parsimonious hypotheses exist to explain the distribution of the derived condition, the elongate urohyal, within the Curimatidae. First, there may have been independent acquisition of the modification in the three lineages, Curimatopsis, Potamorhina, and Psectrogaster. Second, there may have been a single synapomorphic acquisition at the base of the Curimatidae, with secondary shortening of the urohyal occurring independently in Curimata on the one hand and the assemblage consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax on the other. Finally, the elongation may have been acquired at the level of Curimatidae, with a secondary shortening occurring in the clade consisting of Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax, with a secondary lengthening in Psectrogaster.

Each of these hypotheses involves three ad hoc hypotheses about evolutionary events. Given these equally parsimonious alternatives, it was not possible to determine the appropriate phylogenetic levels at which to use these characters as synapomorphies; consequently, they are not incorporated in the cladogram (Figure 44), although the feature was included in the PAUP analysis and has been assigned a synapomorphy number (SYNAPOMORPHY 105) for analysis and discussion purposes.

Basihyal (BH) and Basihyal Tooth Plate (BHTP)

The basihyal is an unpaired median element that extends anteriorly from between the paired dorsal hypohyals. The element typically consists of a cartilaginous core, at least in juveniles, enveloped posteriorly and to varying degrees anteriorly by a sheath of bone. Along its dorsal surface the basihyal may or may not be partially covered by an independent ossification, the thin basihyal tooth plate, that extends anteriorly over the dorsal surface of the cartilaginous portion of the element (Figure 33B). Although the form of the complex formed by the basihyal and basihyal tooth plate varies considerably within the family, the continuum between the majority of morphological states permits the delimitation of only one evidently derived character state.

FIGURE 33.—A, Basihyal of Potamorhina altamazonica, USNM 257367; B, basihyal and basihyal tooth-plate of Steindachnerina bimaculata, USNM 261450. (Dorsal view, anterior at top, dense patterned stippling represents cartilage.)

The majority of curimatids have an elongate to elongate triangular basihyal complex with relatively straight lateral margins (Figure 33A). In Steindachnerina species, rather, the bone-cartilage complex is apomorphously laterally expanded anteriorly, with the anterior cartilaginous portion notably flared outwards. Associated with this reconfiguration of the basihyal is a comparable lateral expansion of the basihyal tooth plate (BHTP, Figure 33B). The anterior expansion of the basihyal and basihyal tooth plate are apomorphous for the species Steindachnerina (SYNAPOMORPHY 100). A similarly expanded basihyal-basihyal tooth plate complex also occurs in the Prochilodontidae, the sister group to the Curimatidae. In light of the unique nature of the Steindachnerina form of the basihyal complex within the Curimatidae and the topology of the most parsimonious phylogenetic scheme in that family (Figure 44), the hypothesis that the expansion of the basihyal and its associated tooth plate in the Prochilodontidae and Steindachnerina represent homoplasies is the most parsimonious.

A basihyal tooth plate is present in the Anostomidae (see Winterbottom, 1980, fig. 45), Prochilodontidae (see Vari, 1983, fig. 22) and Chilodontidae (see Vari, 1983, fig. 24), the immediate sister groups to the Curimatidae. Within the Curimatidae the ossification is variously present at the generic and subgeneric level. Although lacking in Curimatopsis, Potamorhina, and Psectrogaster, that element is found in a minority of Curimata species and in the large majority of the species of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. It would thus appear that the primitive condition within the family is for the ossification to be absent. The presence of a basihyal tooth plate in most members of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is thus considered to be indicative of the monophyly of that assemblage, (SYNAPOMORPHY 94) albeit with qualifications due to the absence of the tooth plate in some members of that lineage.

Branchiostegal Rays (BR1–4)

The Curimatidae, Prochilodontidae, Chilodontidae, and Anostomidae all typically have four branchiostegal rays, although that number is reduced to three in some anostomids (Winterbottom, 1980). The condition in the prochilodontid Semaprochilodus laticeps (Figure 34A) is representative of the generalized condition of the portions of those elements proximate to the hyoid arch in that family. That morphological plan also represents the plesiomorphous condition of those portions of the branchiostegal rays for the Chilodontidae and Anostomidae with respect to the characters of interest in this discussion.

The first two branchiostegal rays in the Prochilodontidae (BR_1 and BR_2) attach to a depression on the ventral surface of the anterior ceratohyal. According to the degree of ossification of the entire hyoid arch, a largely size related function, the area of attachment either has the form of two ossified notches (Figure 34A) or is a broader concave region subdivided by smaller cartilages (Figure 34B). Anterodorsally the margins of the first two branchiostegal rays (BR_1 and BR_2) are slightly convex or straight, but without any pronounced angle proximate to the point of articulation. The third branchiostegal ray (BR_3) attaches to the posterolateral surface of the anterior ceratohyal and only slightly overlaps the posterolateral margin of the second branchiostegal ray leaving the portion of that bone proximate to the anterior ceratohyal exposed laterally.

All members of the Curimatidae demonstrate several derived modifications of the branchiostegal rays that differ from the morphological plan just described. In the Curimatidae the anterodorsal portion of the first and second branchiostegals (BR_1 and BR_2) is dorsally expanded resulting in a pronounced angle in the anterior margin of those bones. As a consequence the margins of these ossifications are distinctly concave proximally, more so in the case of the first branchiostegal ray. The anterodorsal expansion of the proximate portion of the third branchiostegal (BR_3) of curimatids is even more pronounced. This expansion results in the third branchiostegal ray distinctly overlapping the dorsal portion of BR_2 laterally and completely covering the section of that element articulating with the anterior ceratohyal (Figure 34B). In light of the conditions in the proximate outgroups, these modifications of the portions of the first to third branchiostegal rays approximating the hyoid arch are considered apomorphous for the members of the Curimatidae (SYNAPOMORPHY 33).

FIGURE 34.—Hyoid arch (without interhyal) and proximate portion of branchiostegal rays: A, Semaprochilodus laticeps, USNM 270239; and B, Steindachnerina bimaculata, USNM 261450. (Left side, lateral view, anterior to left, dense patterned stippling represents cartilage.)

ANTORBITAL AND INFRAORBITALS

The orbit in the vast majority of characiforms is ringed by a series of eight bones, an antorbital, a supraorbital, and six infraorbitals, with the infraorbitals bearing portions of the laterosensory canal system. Variations in the presence or absence of some of these elements, their relative sizes, and presence and form of the included laterosensory canal segments serve to define subunits of the Curimatidae.

Antorbital

The antorbital (the adnasal of Gregory, 1933, and Daget, 1964), an element lying immediately anterior to the ventral process of the lateral ethmoid, demonstrates only one phylogenetically significant character in the Curimatidae. As noted by Vari (1982a:8) the antorbital is absent in all species of Curimatopsis. The possibility that the absence of the antorbital in Curimatopsis is the result of some paedomorphic process would in first consideration appear likely in light of the relatively small adult size of most species of Curimatopsis. Such an explanation also seems applicable in the case of the diminutive African characid Lepidarchus adonis Roberts which also lacks an antorbital (Roberts, 1966). In Curimatopsis, however, the ossification is absent not only in the diminutive members of the genus such as C. evelynae, but even in a 75.8 mm SL specimen of C. microlepis (USNM 268867) cleared and counterstained for cartilage and bone. Thus the absence of the bone in all Curimatopsis species does not appear to simply represent a paedomorphic feature. Weitzman and Vari (1988) noted that paedomorphosis must be analyzed within a phylogenetic context in which miniaturization and miniatures are evaluated relative to the size and features of those taxa phylogenetically proximate to the potential miniatures. Relative to the much larger body sizes of the Prochilodontidae, and the immediate sequential sister groups to Curimatopsis in the Curimatidae, even the largest Curimatopsis species is of a reduced overall size. Regardless of the underlying cause, the lack of an antorbital is considered a synapomorphy for Curimatopsis species (SYNAPOMORPHY 41).

First Infraorbital (IO[1])

The first infraorbital, the most anterior of that series of bones ringing the ventral and posterior portions of the orbit typically has a discrete tube-like laterosensory canal segment in Characiformes. Within the Curimatidae, a laterosensory canal segment in the first infraorbital is present in the vast majority of species, but is absent in the five species of Curimatopsis, four species of Cyphocharax (gillii, saladensis, punctata, vanderi), and a single species in Steindachnerina (binotata). On the basis of the overall phylogeny, the lack of a laterosensory canal segment in the first infraorbital is considered a synapomorphy that arose independently in Curimatopsis on the one hand (SYNAPOMORPHY 46) and the cited species of Cyphocharax on the other, and which is an autapomorphy for Steindachnerina binotata.

Gregory and Conrad (1938, fig. 28) in their drawing of an unspecified “Curimata” species, illustrate a single canal bearing bone anterior of the lateral ethmoid (their prefrontal plus paraethmoid). That bone, which they identify as the lacrymal, is shown as extending from the supraorbital dorsally around the anterior and anteroventral margins of the orbital rim to the second infraorbital (their second suborbital) posteriorly. The illustrated lacrymal of those authors thus appears to actually represent a combination of two separate bones, the antorbital (that portion of their ossification proximate to the lateral ethmoid) and the first infraorbital (the ventral canal-bearing section of their illustration). Their illustration is also incorrect in showing the infraorbital series posterior of the first infraorbital as a single continuous ossification. In all examined curimatids the second through sixth infraorbitals are discrete elements.

Fourth and Fifth Infraorbitals (IO[4] and IO[5])

The fourth infraorbital commonly contains a tripartite canal in the near relatives of the Curimatidae, the Prochilodontidae (e.g., Ichthyoelephas Posada-Arango, Roberts, 1973, fig. 17), Anostomidae (e.g., Synapotalaemus Myers and Fern´ndez-Yépez, Winterbottom, 1980, fig. 32) and Chilodontidae (e.g., Caenotropus, Géry, 1964b, fig.1). The primary canal segment in this element extends parallel to the anterior margin of the bone along the orbital rim and communicates dorsally and ventrally with comparable canal segments in the fifth and third infraorbitals respectively. The fourth infraorbital also has a horizontal or slightly posteroventrally inclined, posteriorly directed side branch (HC-IO_4) of the laterosensory canal segment. That canal extends posteriorly to the proximity of the opening in the preopercle into the preopercular laterosensory canal system, and sometimes communicates posteriorly with an unossified laterosensory canal segment in the tissue of the adipose eyelid overlying the opercle. The laterosensory canal segment of the fifth infraorbital continues along the arch of the canal segments in the third and fourth infraorbital, without any pronounced angle between the primary axes of the sensory canal segments in the fourth and fifth infraorbitals.

The pattern described above is most common in the Prochilodontidae, Anostomidae, and Chilodontidae, with differences among those families relative to this pattern involving features not pertinent to the Curimatidae. Among curimatids a morphological plan of the fourth and fifth infraorbitals comparable to that of the cited outgroups occurs in Curimatopsis, Potamorhina, Curimata, and Psectrogaster (Figure 35A,B). The genera Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax, in contrast, have the anterior canal segment of the fourth infraorbital (IO_4) more posteriorly angled, with an associated reduction or elimination of the posterior horizontal sidebranch in that bone (HC-IO[4], Figure 35C). The laterosensory canal segment in the fifth infraorbital (IO_5), in turn, is more distinctly angled posteroventrally than in the generalized characiform condition. Together, reorientations of these canals are most obvious in the distinct angle between the primary axes of the laterosensory canal segments in the fourth and fifth infraorbitals; a condition which contrasts with the continuous arch of the canals in those elements in outgroups within (Figure 35A,B) and outside of the Curimatidae (SYNAPOMORPHY 95).

FIGURE 35.—Fourth and fifth infraorbital and dorsal portion of third infraorbital: A, Psectrogaster curviventris, USNM 243221; B, Potamorhina altamazonica, USNM 257367; and C, Curimatella meyeri, USNM 261508. (Left side, lateral view, anterior to left.)

FIGURE 36.—Sixth infraorbital (dermosphenotic): A, Psectrogaster amazonica, USNM 261518; B, Potamorhina altamazonica, USNM 257367; C, Curimata cyprinoides, USNM 267964; and D, Steindachnerina conspersa, USNM 232224. (Left side, lateral view, anterior to left.)

Most species of Potamorhina retain the plesiomorphous orientation of the fourth and fifth infraorbitals and their canals. The fourth and fifth infraorbitals in that genus are, however, unique within the Curimatidae in their pronounced posterior development. This is particularly the case for the fourth infraorbital and the horizontal laterosensory canal segment in that ossification, with these shifts in the relative positions of those canals considered together to be an apomorphy for the genus (SYNAPOMORPHY 45). Potamorhina pristigaster, which shares with its congeners the posterior expansion of the fourth infraorbital also has the form of the laterosensory canal segments in the fourth and fifth infraorbitals autapomorphously modified. That species has a distinct acute angle between the laterosensory canal segments in the fourth and fifth infraorbitals reminiscent of the condition in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. That decreased angle between the axes of the canals in these bones is a consequence of the posterior repositioning of the two ossifications relative to the orbital rim. The condition differs significantly from the reduced angle between the canal segments in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax which results from the reorientation of the canal segments in the fourth and fifth infraorbitals which have not themselves been shifted posteriorly from the orbital rim in those taxa. Thus the P. pristigaster condition is considered an autapomorphy non-homologous with the situation in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

Sixth Infraorbital (IO[6])

The sixth infraorbital (the dermosphenotic of some authors) is an independent ossification that roofs over the dilatator fossa on the lateral surface of the neurocranium. The generalized condition of the ossification in characiforms has a tripartite laterosensory canal system comparable to that of Figure 36A,B, with the ventral arm of the complex contacting the laterosensory canal segment in the fifth infraorbital (IO_5). The posterodorsal branch of the IO_6 canal system (PD) approximates the anterior opening of the pterotic sensory canal, and the anterior branch extends anterodorsally to the frontal. Such a condition of the laterosensory canal system in the sixth infraorbital is the basic pattern in the Prochilodontidae, Anostomidae, and Chilodontidae, along with a variety of other characiforms including members of the Old World families Citharinidae (Citharinus, Daget, 1962a, fig, 7; Citharidium Boulenger, Daget, 1962b, fig. 10), Distichodontidae (Xenocharax, Daget, 1960, fig. 7; see also Vari, 1979:296–301 for the remainder of the family), Hepsetidae (Roberts, 1969, fig. 1), and Characidae (Hydrocynus, Allis, 1905, fig. 13). In the Neotropical realm a similar morphology of the sixth infraorbital is found in many, although not all, members of the Characidae (e.g., Brycon, Weitzman, 1962, figs. 8, 9), Hemiodontidae, and Erythrinidae (e.g., Hoplias, Roberts, 1969, fig. 3) among other families.

Several modifications of the sixth infraorbital and its enclosed laterosensory canal segment define subunits of the Curimatidae. The relative size of the sixth infraorbital is reduced in Curimatopsis microlepis and C. macrolepis. The three remaining species of the genus (evelynae, crypticus, and myersi) demonstrate no trace of an ossified sixth infraorbital. As adults these latter species are some of the smallest in the family and it is possible that the reduced sixth infraorbital represents a paedomorphic event characteristic of the clade. That possibility is particularly notable since the sixth infraorbital is absent in a number of diminutive characiforms (see Weitzman and Fink, 1983, fig. 24, and Weitzman and Fink, 1985:63, fig. 54). Nonetheless it is noteworthy that cleared and stained specimens of Curimatopsis crypticus of 42.1 mm SL show no indication of an ossified sixth infraorbital although the element is present in comparably sized individuals of other curimatid species that achieve larger adult body sizes. Regardless of the process underlying the lack of an ossified dermosphenotic in these taxa, that absence is considered derived and a synapomorphy for the clade consisting of Curimatopsis evelynae, C. myersi, and C. crypticus (Curimatopsis SYNAPOMORPHY F). Similarly the combination of a reduction or loss of that bone is hypothesized to be synapomorphous for the entire genus (SYNAPOMORPHY 42).

Within the Curimatidae, two clades at the generic and suprageneric levels are definable by derived states of the sixth infraorbital and its contained laterosensory canal segment. The elaboration of the plesiomorphous tripartite IO_6 laterosensory canal segment via the addition of a posteroventral and sometimes also anteriorly and anteroventrally aligned side branches (Figure 36C) was discussed by Vari (1984a:6). That condition, synapomorphous for the species of Potamorhina (SYNAPOMORPHY 67), is not analyzed again here.

Whereas a tripartite canal system in the sixth infraorbital or an elaboration of that pattern are common to species of Curimatopsis with that element, along with Potamorhina, Curimata, and Psectrogaster, all other curimatids have only a single unbranched laterosensory canal segment in that ossification (Figure 36D). That simplified straight canal segment communicates with the fifth infraorbital sensory canal (IO_5) ventrally, and extends dorsally to approximate the anterior opening of the pterotic sensory canal, lacking any contact with the laterosensory canal segment in the frontal. Given the generality of a tripartite laterosensory canal segment in the sixth infraorbital of proximate curimatid outgroups and among characiforms as a whole, the simple laterosensory system in the sixth infraorbital in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is hypothesized as derived (SYNAPOMORPHY 96).

OPERCULAR APPARATUS

Opercle and Subopercle

The close morphological and functional association of the opercle and subopercle makes it most efficient to discuss these elements jointly. The Curimatidae as a whole demonstrates a posteroventral truncation of the opercle and the associated expansion of the subopercle relative to the condition of these elements in examined outgroups. These modifications are, however, difficult to quantify non-arbitrarily, and thus I prefer not to utilize them as synapomorphies for the members of the Curimatidae, a clade that is already delimited by numerous uniquely derived characters. Within the Curimatidae, the opercle is significantly expanded posteriorly in all Potamorhina species relative to the condition in the outgroups. That expansion of the opercle in conjunction with the overall posterodorsal reorientation of the originally vertical primary axis of the opercle results in a pronounced inclination of the line of junction between the opercle and subopercle (see Vari, 1983, fig. 22). These modifications in the overall form and relative position of the opercle are together considered to be a synapomorphy for the species of Potamorhina (SYNAPOMORPHY 73).

Interopercle

The interopercle, the element lying ventral of the preopercle, and anterior of the subopercle and the anteroventral portion of the opercle is modified to some degree in all curimatids relative to the condition in the outgroups and also demonstrate a degree of variability within the family. In proximate outgroups to the Curimatidae the ossification is only vertically developed to a moderate extent in the region where it abuts the opercle and subopercle (see Winterbottom, 1980, fig. 33 for Anostomidae; Géry, 1964b, fig. 1 for Chilodontidae; and Vari, 1983, fig. 28 for Prochilodontidae). A somewhat more pronounced development posteriorly of the interopercle is typical for all curimatids. The intrafamilial variation in the form of the interopercle makes it difficult to non-arbitrarily define discrete characters within that continuum. Thus this feature is not used as a synapomorphy for the species of the family, which share numerous other synapomorphies.

The continuum between the forms of the interopercle within the Curimatidae also makes it difficult to non-arbitrarily discriminate character states for this element. As a consequence it is possible to only recognize readily a single derived condition of the interopercle within the family. In all Potamorhina species the interopercle is significantly further developed posteriorly into a triangular plate filling the space between the rear of the preopercle and the anterior margin of the opercle and subopercle (see Vari, 1983, fig. 22). This apomorphous expansion is considered a synapomorphy for Potamorhina (SYNAPOMORPHY 74).

LIGAMENTUM PRIMORDIALE

The A_1 section of the adductor mandibulae muscle in curimatids extends anteriorly from the preopercle to an attachment on the posterdorsal portion of the lower jaw. Arising from the anterodorsal portion of the adductor mandibulae and the proximate portions of the angulo-articular is a tendonous band that extends anterodorsally to an insertion either on the posterior margin (Curimatopsis species) or the medial surface of the main portion of the maxilla (all other curimatids). The ligament gradually tapers dorsally, without any marked shift in form or size. That band, the ligamentum primordiale (the primordial ligament of Winterbottom, 1974:232, and the articular-maxillary ligament of Alexander, 1964:183), arises in most characiforms from an aponeurotic sheet on the anterodorsal portion of A_1 and the proximate portions of the angulo-articular.

Although the area of origin of the ligament and the degree of its association with the angulo-articular varies within characiforms, the described morphology of the band is typical for all examined outgroups in the order. Within the Curimatidae such a relatively straight, cord-like ligamentum primordiale is found only in the species of Curimatopsis. All the remaining members of the family have the ligamentum primordiale complex modified to varying degrees. The species of Potamorhina and Curimata have the aponeurotic sheet on the anterodorsal portion of A_1, that typically serves as the origin of the ligamentum primordiale greatly expanded into a discrete thick connective tissue mass at the base of the main portion of the ligament. That thickening lies proximate to and is anteroventrally attached by connective tissue to the posterodorsal margin of the angulo-articular but structurally remains relatively distinct from the lower jaw.

This expanded ventral portion of the ligamentum primordiale complex in Curimata and Potamorhina is further modified in the genera Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. Those taxa have a discrete dense mass centered along the longitudinal axis of the ligament. That body largely replaces the expanded fibrous connective tissue body found on the proximal section of the ligamentum primordiale in Curimata and Psectrogaster. Histological examination has shown that the body included in the ligamentum primordiale consists of cartilage enclosed within a aponeurotic sheet of varying thickness (Figure 37). The anterior portion of the cartilage serves as an area of attachment for a relatively extensive portion of the ligamentum primordiale. Posteriorly the cartilage body is continuous with the tendenous fibers of the anterior portion of the A_1 section of the adductor mandibulae muscle. The entire cartilage-ligament complex attaches via loose ligamentous bands to the posterodorsal margin of the angulo-articular. As is the case of the thickened connective tissue body in Curimata and Potamorhina, the ligamentum primordiale cartilage in Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is not directly associated with the lower jaw.

FIGURE 37.—Ligamentum primordiale, cartilage body of ligamentum primordiale, and proximate portions of A_1 section of adductor mandibulae muscle, maxilla, dentary, and angulo-articular of Steindachnerina bimaculata, USNM 261450. (Jaws in open position, continuation of ligamentum primordiale medial to maxilla indicated by dashed lines, right side, lateral view, anterior to right, dense patterned stippling represents cartilage.)

These modifications and elaborations of the proximal portions of the ligamentum primordiale are unique to the cited genera of the Curimatidae among examined characiforms and are considered to represent synapomorphies at two different levels of universality within the Curimatidae. The possession of some form of elaboration of the proximal portion of the ligamentum primordiale, either with or without an included cartilage body, is hypothesized to be a synapomorphy for the genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 58). The presence of a cartilage mass in the ligamentum primordiale connective tissue complex is, in turn, hypothesized to be a further derived synapomorphy for the assemblage consisting of Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 84).

UPPER AND LOWER JAWS

The most obvious distinguishing character of the curimatid jaws, upper and lower, is the absence of oral dentition in adults of the family. Juveniles of Curimata cyprinoides of up to approximately 25 mm SL have a single row of unicuspidate teeth in each jaw. Comparable dentition has been reported for Steindachnerina elegans by Azevedo et al. (1938, figs. 1, 2) and for several upper Rio Paraná curimatid species by de Godoy (1975:589, 596, 601). As juveniles of the Curimatidae alter their diet from zooplankton to detritus, this larval dentition is completely lost in all specimens above 30 mm SL. The vast majority of characiforms have some form of dentition, typically well developed, as adults and the absence of jaw teeth in adult curimatids is considered a synapomorphous reduction for the family (SYNAPOMORPHY 16).

The only other members of the Characiformes lacking jaw teeth as adults are Anodus elongatus Spix and Eigenmannina melanopogon (Cuvier) of the Hemiodontidae. As noted under “Synapomorphy List and Phylogenetic Reconstruction,” this similarity is considered to represent a homoplasious loss of teeth in the hypothesized ancestoral species of the Curimatidae and in the lineage consisting of Anodus and Eigenmannina in the Hemiodontidae rather than a synapomorphy of Curimatidae and those taxa.

Premaxilla (PMX)

The premaxillae of curimatids are joined across the midline by connective tissue bands and attached to the ethmoid both through broad connective tissue sheets and via discrete ligaments. The range in the relative size and overall position of the mouth in different subunits of the family is reflected in the variety of premaxillary forms found among curimatids. Most of this variation, however, forms a continuum that is difficult, if not impossible, to non-arbitrarily subdivide into discrete units and thus it is not readily used in phylogenetic analyses. Two different discrete modifications of the premaxilla are recognizable, however, and serve to delimit assemblages of genera within the Curimatidae.

The premaxilla of the proximate outgroups to the Curimatidae, the families Prochilodontidae, Anostomidae and Chilodontidae, are all apomorphously modified in overall form (Vari, 1983:9) making them inappropriate as outgroups for evaluating the plesiomorphous form of the premaxilla among curimatids. As a consequence more distant outgroups, albeit of inexact phyletic position relative to the Curimatidae, were utilized. These examinations have shown that the generalized condition of the premaxilla in those characiform outgroups is a relatively well developed bone with a definite triangular form in dorsal or anterodorsal view. Such a premaxilla is characteristic of the vast majority of curimatids. The members of the genus Curimatopsis, alternatively, have an extremely elongate premaxilla that gradually tapers laterally to a curved rod-like shaft. The unique nature of this form of premaxilla within the Curimatidae and proximate outgroups results in its being considered a synapomorphy for the members of Curimatopsis (SYNAPOMORPHY 47).

The second alteration of the premaxilla that characterizes a subunit of the Curimatidae involves the mode of articulation between the premaxilla and maxilla. The posteroventral margin of the premaxilla extends a short distance lateral to the anterior margin of the main body of the maxilla. The point of contact between those elements in Potamorhina, Psecterogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax is elaborated into a discrete joint with an articular facet on both the premaxilla and maxilla at their point of contact. These modifications of the two bones at their area of articulation is considered to be a synapomorphy for the genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax given the absence of such structures in the examined characiform outgroups (SYNAPOMORPHY 59).

Maxilla (MX)

The maxilla, the second element of the upper jaw, demonstrates a number of discrete modifications within the Curimatidae, several of which are pertinent to the generic-level phylogeny in the family. Outgroup comparisons to determine the plesiomorphous condition of the maxilla within the Curimatidae are obscured by the apomorphous modifications of the maxilla in each of the proximate sister groups of the Curimatidae (Prochilodontidae, Anostomidae, and Chilodontidae). Outgroup comparisons to more distantly related characiform taxa of uncertain phylogenetic relationship relative to the clade formed by those three families and the Curimatidae nonetheless allow the advancement of a hypothesis of the generalized condition of the bone. Based on those comparisons, the generalized characiform condition of the maxilla is considered herein to be a moderately developed, laterally flattened blade-like body ventrally which is continuous dorsally with the dorsal rod-like articular process (e.g., various glandulocaudine species, Weitzman and Fink, 1985, figs. 59–66). Such a form of the maxilla is not encountered in the Curimatidae but a variety of derived overall morphologies of the bone do characterize subunits of the family.

Curimatopsis has a paddle-shaped, laterally flattened main body of the maxilla. The attachment of the ligamentum primordiale (LP) onto the maxilla is at the rear of the ossification in the area where the dorsal process of the maxilla joins the main body of the bone (AI, Figure 38A). Such an area of attachment is generalized for examined characiforms including the Anostomidae and Chilodontidae and is thus considered plesiomorphous. As a consequence of the highly modified form of the oral jaws in the Prochilodontidae, it is not possible to utilize the condition in that family for outgroup comparisons. The anteriorly expanded paddle-shaped main body of the bone characteristic of Curimatopsis, in contrast, is encountered in only a few characiform outgroups (e.g., Thrissobrycon pectinifer Böhlke, 1953, fig. 1). In light of its unusual nature within characiforms the condition of the maxilla in Curimatopsis is consequently considered a synapomorphy for the species of Curimatopsis (SYNAPOMORPHY 48).

The species of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax have a dramatically different morphology of the maxilla. In all the species of those genera the anterior margin of the bone is only slighly developed, often with a notch to accommodate the lateral portion of the premaxilla (N, Figure 38B). The posterodorsal portion of the main body of the maxilla, alternatively, is developed into a large plate-like process (PP) that extends under the first infraorbital when the mouth is closed. The attachment of the ligamentum primordiale in these taxa (AI) is now on the medial surface of the maxilla at the anterior margin of this expanded posterodorsal process. Utilizing that point of attachment as a homologous landmark, it appears that the posterodorsal process of the maxilla is the consequence of an expansion of that region of the bone. Given the absence of such a process on the maxilla in other examined characiforms, the possession of that structure is considered derived and a synapomorphy for the genera Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 60). As noted above, these taxa also have in common the derived possession of an articular facet on the dorsal margin of the maxilla which contacts a comparable process on the premaxilla.

FIGURE 38.—Maxilla and anterodorsal portion of ligamentum primordiale: A, Curimatopsis microlepis, USNM 268867; and B, Psectrogaster ciliata, USNM 269990. (Left side, lateral view, anterior to left, area of insertion of ligamentum primordiale on maxilla not obvious in lateral view, point on lateral surface overlying insertion indicated by “AI”.)

Dentary (DEN)

The dorsal margin of the dentary bone typically is anteriorly straight or slightly convex, and posteriorly distinctly convex in the proximate outgroups to the Curimatidae, the families Prochilodontidae, Anostomidae and Chilodontidae (see Vari, 1983, fig. 2). That condition, hypothesized as plesiomorphous for the Curimatidae, is also found in the family in all members of Curimatopsis (Figure 39A). The remainder of the family Curimatidae, in contrast, has a sigmoid dorsal margin to the dentary, with the convex central portion of the bone flanked by two concave regions (Figure 39B). The centrally convex region, hypothesized as derived relative to the condition in Curimatopsis and the outgroups to the Curimatidae, is thus considered a synapomorphy for Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 61). It demonstrates notable variation within the family. In some taxa (e.g., Curimata) it is developed into a distinct, somewhat triangular process, whereas in others (e.g., Potamorhina) it curves laterally into a bony lip. The non-Curimatopsis. curimatids cannot feasibly be non-arbitrarily divided into discrete subsets based on this variation. I consequently will not utilize those differences at less inclusive phylogenetic levels.

FIGURE 39.—Lower jaw: A, Curimatopsis microlepis, USNM 268867; and B, Curimatella alburna, MZUSP 6309. (Left side, lateral view, anterior to left.)

PALATINE ARCH

The palatine arch consists of four bones, the palatine, ectopterygoid, mesopterygoid, and metapterygoid, and their associated cartilages. In the majority of characiforms those elements form a closely interconnected complex extending between the upper jaw, ethmo-palatine cartilage and vomer anterodorsally, the quadrate ventrally and the hyomandibula posteriorly. Each of the components of the palatine arch demonstrates derived modifications pertinent to the question of the monophyly of the Curimatidae and various subunits of that family. In order to simplify the discussion and evaluation of the polarities of each of these alterations, the morphology of each component of the arch will be discussed individually.

Palatine (PAL) and Ethmo-palatine Cartilage (EPC)

One character of the palatine synapomorphous for all the species of the Curimatidae was previously discussed in detail by Vari (1983:26). The most common condition of the palatine in characiform outgroups has a single anterodorsal cartilaginous articular surface contacting the vomerine region of the neurocranium and the ethmo-palatine cartilage associated with the upper arm of the premaxilla (the submaxillary cartilage of Daget, 1964, fig. 23). All species of the Curimatidae differ from that hypothesized plesiomorphous arrangement in having an additional, distinct cartilage-capped process on the posterodorsal surface of the bone (PDAS, Figure 40A,B). That cartilage articulates with a corresponding process on the anteroventral surface of the ventral wing of the lateral ethmoid (Vari, 1983, fig. 25). Although a second articular surface on the palatine somewhat comparable to that in the Curimatidae is approximated to varying degrees in some characiform outgroups, both in the Neotropical and Ethiopian realms, such a structure is absent in the proximate outgroups to the Curimatidae, the families Prochilodontidae, Anostomidae, and Chilodontidae. The absence of a cartilage capped-articular surface contacting the lateral ethmoid in those taxa in conjunction with the morphological differences in the form of similar processes in those characiform outgroups with such modifications is congruent with the hypothesis that the posterodorsal articular process of the palatine characteristic of the Curimatidae (SYNAPOMORPHY 21) is derived for that family (see Vari, 1983:26, for a more detailed discussion).

Within the Curimatidae, the palatine shows a second set of modifications that are common to Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. All species of Curimatopsis (Figure 40A) have a continuous elaborate cartilage that extends along the anterior face of the palatine (PAL), continues along the dorsomedial margin of the bone, and expands posterodorsally into the distinct secondary articular process (PDAS) described above. The cartilage then continues posteroventrally along the lateral surface of the palatine arch in the region of contact of the metapterygoid and ectopterygoid. In Potamorhina, Psectrogaster, Curimata, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax the continuous palatine cartilage characteristic of Curimatopsis is subdivided into two discrete portions separated by a well ossified posteromedial region of the palatine (Figure 40B). Anteriorly and laterally the anterior cartilage articulates with the ethmo-palatine cartilage (EPC) and the vomer respectively. That cartilage is also characterized by a distinct central depression (Figure 40B) that is not present in Curimatopsis. The posterodorsal palatine articular cartilage (PDAS) is a discrete mass enveloped anteriorly, medially, and to varying degrees laterally by the ossified surface layer of the palatine. Ventrolaterally the posterolateral articular surface retains its continuity with the cartilaginous band overlying the junction between the metapterygoid and the ectopterygoid (Figure 40B). This subdivision of the palatine cartilage into two articular surfaces and the associated complex restructuring of the ossified portions of that element are unique to this assemblage of genera among examined characiforms and considered a synapomorphy for Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 62).

FIGURE 40.—Palatine, ethmo-palatine cartilage and proximate portions of premaxilla and metapterygoid: A, Curimatopsis microlepis, USNM 268867; and B, Steindachnerina argentea, USNM 285663. (Right side, dorsal view, anterior to left, dense patterned stippling represents cartilage.)

The ethmo-palatine cartilage (EPC) is a distinct body situated between the posterior surface of the upper arm of the premaxilla and the anterior margin of the palatine. There is usually only a single cartilage mass lying between these bones, although that cartilage is apparently subdivided into two units in some taxa (e.g., the Old World characiform family Citharinidae, Vari, 1979:294). The ethmo-palatine cartilage is usually a relatively well developed thick body extending along most of the anterior margin of the palatine and much of the rear of the dorsal process of the premaxilla (e.g., Steindachnerina argentea, Figure 40B) to which it is relatively closely joined by connective tissue bands. Such a condition is found in the genera Potamorhina, Psectrogaster, Curimata, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. In the species of Curimatopsis, in contrast, the ethmo-palatine cartilage is reduced to a very small ovoid body along the posteromedial surface of tip of the premaxilla (Figure 40A). That condition represents a significant reduction in the relative size of the cartilage that is considered a synapomorphy for the members of the genus (SYNAPOMORPHY 49).

Ectopterygoid (ECT)

The ectopterygoid shows a wide range in overall morphology within the Curimatidae, although most of the variation cannot be non-arbitrarily apportioned into discrete characters. One distinct difference, distinguishing Curimatopsis from the remainder of the family, involves the form of the anterior margin of the ectopterygoid. That region of the bone is unelaborated and transversely rounded in the species of Curimatopsis but has a distinct flattened vertical flange in Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. The condition of the elements in Curimatopsis is similar to that in most characiforms, and within the context of such an outgroup analysis would be evaluated as being plesiomorphous. The Prochilodontidae, the sister group to the Curimatidae, however, has a highly modified ectopterygoid that is distinctly flattened transversely. It is thus possible that the flange along the anterior margin of the bone in non-Curimatopsis curimatids is at least in part homologous with the anterior portion of the flattened prochilodontid ectopterygoid. If that is the case, then the Curimatopsis form of the ossifications would be a derived secondary reversal to the more generalized condition. Both hypotheses, that the Curimatopsis form of the ectopterygoid is derived, or that it is plesiomorphous, would be congruent with the proposed overall most parsimonious phylogeny. Thus it is not possible to polarize the character by either outgroup comparisons or by reference to the overall most parsimonious hypothesis of intrafamilial relationships.

Mesopterygoid (MES)

The mesopterygoid is typically a relatively simple ossification situated between the palatine and metapterygoid, and lying dorsal of the quadrate (Figure 41A). The relative size of the element varies in different groups of characiforms, with the condition in the proximate outgroups to the Curimatidae being a small to moderate sized bone that is unelaborated along its dorsal margin. The mesopterygoid and metapterygoid which lie posterior to it along the palatine arch, are suspended from the neurocranium by a broad thin connective tissue sheet that attaches along the length of the dorsal margins of those ossifications.

The described suspensory system joining the mesopterygoid to the cranium is modified in all curimatids. Members of that family rather than retaining a broad connective tissue band between those regions, have instead a discrete ligamentous band that extends between the dorsal margin of the mesopterygoid and the ventral surface of the vomer. Within the Curimatidae, this ligamentous band has two different shapes and forms of attachment to the mesopterygoid. In Curimatopsis, the ligamentous band is quite narrow dorsally, but progressively fans out ventrally to attach over a relatively broad region of the dorsal margin of the mesopterygoid. In Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax the ligament arises in a similar fashion from the vomer, but does not fan out ventrally, being rather more strap-like and of continuous width from the vomer to the mesopterygoid and attaching onto the latter element on a distinct dorsal process (AI, Figure 41A,B).

Thickenings within the broad connective tissue sheet between the palatine arch and neurocranium standard for most characiforms are found in various taxa, including the genus Ichthyoelephas in the Prochilodontidae. Those ligamentous bands, however, are not as discrete as those within the Curimatidae, nor do they have the same areas of attachment. Thus those structures are considered non-homologous with the discrete ligament between the vomer and mesopterygoid characteristic of the Curimatidae. Given the broad area of attachment of the connective tissue sheet typically joining the palatine arch and the neurocranium in characiforms, these reductions in the area of attachment of the connective tissues extending between the vomer and mesopterygoid in curimatids are treated as derived.

In the Curimatidae, such reductions in the area of attachment are considered apomorphous at two levels of universality. The possession of a fan-shaped or strap-like thickened connective tissue band arising from a restricted area on the vomer and having either a broad or narrow attachment on the mesopterygoid is hypothesized a synapomorphy for all members of the Curimatidae (SYNAPOMORPHY 34). The presence of a strap-like ligament of constant width with a discrete further restricted area of attachment to the mesopterygoid, in comparison with the more extensive area of attachment in Curimatopsis and characiform outgroups, is, in turn, hypothesized to be a shared derived character for Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 63).

The mesopterygoid in characiforms most commonly lies dorsal of the junction of the posterodorsal portion of the quadrate and the anteroventral region of the metapterygoid, with those elements meeting along a synchondral joint below the mesopterygoid. A majority of characiforms have a moderately to well developed aperture, the metapterygoid-quadrate fenestra (MQF, Figure 41A), delimited anteriorly and ventrally by the quadrate (QU), dorsally and posteriorly by the metapterygoid (MET) and sometimes posteroventrally by the symplectic (SYM) (e.g., Brycon meeki, Weitzman, 1964, fig. 10). Such an association of bones and cartilages is considered plesiomorphous in light of comparisons to both proximate outgroups to the Curimatidae and diverse other characiforms. Within the Curimatidae that pattern of bones also occurs in the species of Curimatopsis and Potamorhina (Figure 41A). The species of Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax have the mesopterygoid significantly modified. In those genera, the mesopterygoid no longer terminates ventrally distinctly short of the dorsal margin of the metapterygoid-quadrate fenestra. Rather the mesopterygoid is further expanded ventrally over the medial surface of the junction of the metapterygoid and quadrate and continues partially or completely across the anterior portion of the metapterygoid-quadrate fenestra (Figure 41B). This extension of the mesopyterygoid results in the subdivision of that fenestra to varying degrees into anterior (ASMQF) and posterior (PSMQF) sections. Such an elaboration of the mesopterygoid, and the assocated subdivision of the metapterygoid-quadrate fenestra has not been encountered in any examined characiform outgroups. That ventral expansion of the mesopterygoid is consequently considered a synapomorphy for the clade consisting of Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 85).

FIGURE 41.—Mesopterygoid: A, Potamorhina laticeps, USNM 121325; and B, Psectrogaster ciliata, USNM 26990. (Right side, medial view, anterior to left, proximate portions of neighboring bones outlined and lightly stippled.)

Metapterygoid (MET)

Vari (1983:28) noted that members of the Curimatidae have an apomorphous elaboration of the metapterygoid consisting of a ridge extending along the medial surface of the bone for at least part of its length. That condition, hypothesized to be a synapomorphy for the members of the Curimatidae (SYNAPOMORPHY 23), is further developed in various sublineages of the family. The ridge (METR) is only moderately developed in Curimatopsis (Figure 42A) and Potamorhina (Figure 42B), but is much more pronounced in Curimata (Figure 42D), Psectrogaster (Figure 42C), Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax in which it extends across the entire length of the bone. This more extensive development of the metapterygoid ridge is hypothesized to be a more derived condition in light of the absence of any form of the ridge in examined outgroups and relative to the less developed ridge in Curimatopsis and Potamorhina. The possession of such a process is thus considered a synapomorphy for Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 77).

The species of Curimata have the ridge on the medial surface of the metapterygoid considerably thickened anteriorly (Figure 42D). This expanded region of the bone is continuous anteriorly with the comparably expanded region on the posteromedial portion of the mesopterygoid that serves as the area of attachment for the ligament extending between that element and the vomer. This expansion of the anterior portion of the metapterygoid, unique to the species of Curimata, is hypothesized synapomorphous for the genus (SYNAPOMORPHY 83).

FIGURE 42.—Metapterygoid: A, Curimatopsis microlepis, USNM 268867; B, Potamorhina altamazonica, USNM 257367; C, Psectrogaster ciliata, USNM 269990; and D) Curimata cyprinoides, USNM 267964. (Right side, medial view, anterior to left, proximate portions of neighboring bones outlined and lightly stippled.)

As noted in the discussion of the mesopterygoid in the previous section, the metapterygoid and quadrate jointly delimit a usually relatively large, rotund, or horizontally oblong aperture in the middle portion of the suspensorium. That opening, the metapterygoid-quadrate fenestra, is widely distributed within the Characiformes, being found in the Neotropical Characidae (Brycon, Weitzman, 1962:46, fig. 10; Acestrorhynchus Eigenmann and Kennedy, Roberts, 1969, fig. 32), Ctenoluciidae (Ctenolucius Gill, Roberts, 1969, fig. 28), Erythrinidae (Hoplias, Roberts, 1969, fig. 29), Hemiodontidae (Hemiodus, Roberts, 1974, fig. 7), Parodontidae, Prochilodontidae (Ichthyoelephas, Vari, 1983, fig. 28), and Anostomidae (Winterbottom, 1980, fig. 35), and in the Old World families Characidae (Alestes, Hydrocynus [Brewster, 1986, fig. 8], and Phenacogrammus), Hepsetidae (Hepsetus Swainson), Citharinidae (Citharinus, Daget, 1962a, fig. 9; Citharidium, Daget, 1962b, fig. 13), and most members of the Distichodontidae (Xenocharax, Daget, 1960, fig. 10). Although this fenestra is subdivided by a posteroventral process of the mesopterygoid in most genera of the Curimatidae (see previous section), the overall form of opening characteristic of most characiforms is found in all curimatids other than the species of Curimatopsis. In that genus the fenestra is nearly erradicated by the ventral expansion of the metapterygoid which extends nearly to the dorsal margin of the posterior portion of the quadrate (Figure 42A). This reduction in the extent of the aperture differs from the diminished opening in some members of the Old World characiform family Distichodontidae in the mode in which it is achieved. In the distichodontid Neolebias spilotaenia Boulenger the reduced fenestra is a consequence of the expanded symplectic rather than an enlarged metapterygoid (Vari, 1979:293). Nannocharax Günther and Hemigrammocharax Pellegrin of the same family (see Daget, 1961, fig. 10), along with members of the Neotropical family Lebiasinidae (see Weitzman, 1964, fig. 7) have the quadrate approximating the metatperygoid as a consequence of the reduced vertical extent of the entire suspensorium rather than due to an expansion of individual elements. The conditions in those outgroup families thus all differ from that found in Curimatopsis.

A near or total elimination of the fenestra by an expanded metapterygoid is found, however, in all members of the Chilodontidae. The closest relatives to the Chilodontidae, the family Anostomidae is, in contrast, characterized by the presence of a fenestra (see Winterbottom, 1980, fig. 35). Similarly the Prochilodontidae, the sister group to the Curimatidae, has a complete metapterygoid-quadrate fenestra typical of characiform outgroups (e.g., Ichthyoelephas, Vari, 1983, fig. 28) as do all curimatids other than Curimatopsis. It is thus most parsimonious to assume that the conditions in the Chilodontidae and Curimatopsis are homoplasious. The Curimatopsis condition of a reduction of the metapterygoid-quadrate fenestra as a consequence of the expansion of the metapterygoid is thus considered a synapomorphy for the members of the genus (SYNAPOMORPHY 39).

SUPRANEURALS (SN1–6)

A series of midsagittal ossifications are typically found dorsal of the vertebral column in the region between the rear of the neurocranium and the anteriormost proximal radial pterygiophore of the dorsal fin. These bones, the supraneurals, along with the proximal radial pterygiophores of the dorsal fin interdigitate basally between the distal portions of the neural spines of the proximate vertebrae. In the following discussion and in Figure 43 neural spines are numbered sequentially from the spine of the first free vertebrae posterior of the Weberian complex.

The typical pattern for these elements in the Curimatidae is that shown in Figure 43A. Two supraneurals are located anterior of the first neural spines (the two anterior supraneurals are sometimes fused), with the third to fifth supraneurals and the second to fourth neural spines interdigitating sequentially. The basal portion of the first proximal radial pterygiophore of the dorsal fin interdigitates between the distal portions of the fourth and fifth neural spines. This pattern of supraneurals, neural spines, and the first proximal pterygiophore is generalized for the vast majority of curimatid species with three exceptions. Two nominal species in Curimata (vittata and murieli) have the number of supraneurals reduced to four. This reduction is apparently a consequence of the loss of the posterior supraneural, and as a consequence the most posterior element of that series in these species is located between the second and third neural spines. Associated with that reduction in the number of supraneurals is the shift anteriorly of the region of interdigitation of the basal portion of the first proximal pterygiophore of the dorsal fin to between the third and fourth neural spines, rather than between the fifth and sixth spines.

The species of Pseudocurimata have the opposite modification of the pattern of association of the supraneurals and the anterior proximal radial pterygiophore with the anterior neural spines. In that genus the anterior proximal pterygiophore of the dorsal fin inserts between the distal portions of the fifth and sixth, or sixth and seventh neural spines rather than between the fourth and fifth neural spines as in the vast majority of curimatids. Associated with that more posterior insertion of the fin is the absence of a supraneural or proximal pterygiophore either between the fourth and fifth, or fifth and sixth neural spines (Figure 43B,C).

FIGURE 43.—Supraneurals, neural spines of proximate vertebrae, and first proximal radial pterygiophore of dorsal fin: A, Curimata cyprinoides, USNM 225619; B, Psuedocurimata lineopunctata, MCZ 54029; and C, Pseudocurimata peruana, USNM 285667. (Left side, lateral view, anterior to left.)

Outgroup information on the polarity of the different patterns of interdigitation is equivocal. Various species in the Prochilodontidae have the first proximal pterygiophore of the dorsal fin inserting either between the fourth and fifth or fifth and sixth neural spines, and demonstrate overall patterns of supraneurals, neural spines, and proximal pterygiophores comparable to those shown in Figure 43A,B. Members of the Anostomidae also show some variation in the interdigitation pattern of these elements, whereas the species of the Chilodontidae have the first proximal pterygiophore inserting between the fourth and fifth neural spines, with the overall pattern of that element, the neural spines, and supraneurals similar to the pattern of Figure 43A. Given the distribution of the various states within the Curimatidae and in its sister groups of varying degrees of proximity, it is most parsimonious to hypothesize that the position of the first proximal pterygiophore of the dorsal fin posterior of the fifth or sixth neural spines in Pseudocurimata is derived (SYNAPOMORPHY 102).

Such a posterior portion of the dorsal fin and the resultant gap in the sequence of interdigitations of elements between the neural spines immediately anterior to the first proximal pterygiophore of the dorsal fin that is general to all Pseudocurimata species also occurs in two other nominal species within the Curimatidae. Curimata ocellata and C. semitaeniata, elongate fusiform species of the Amazon basin have a pattern of supraneurals and the anterior proximal pterygiophore of the dorsal fin comparable to that of some Pseudocurimata species (e.g., Pseudocurimata lineopunctata, Figure 43B). The common occurrence of this derived pattern in Curimata ocellata and C. semitaeniata on the one hand, and Pseudocurimata species on the other is considered homoplasious within the context of the overall most parsimonious hypothesis of relationships.

CAUDAL FIN COMPLEX

The hypural complex and the rays of the caudal fin demonstrate a number of apomorphous modifications in Curimatopsis which were previously discussed and illustrated by Vari (1982a:5–9). Four of those characters involve sexually dimorphic features in which the derived condition is found only in the males. These apomorphies are the expansion of the posterior neural and haemal spines on the posterior two free centra into broad midsaggital plates (see Vari, 1982a, figs. 2, 4; SYNAPOMORPHY 35), the possession of basal spurs on the middle caudal-fin rays (see Vari, 1982a, fig. 5; SYNAPOMORPHY 36), the vertical expansion of the penultimate ray of the lower lobe of the caudal fin (see Vari, 1982a, fig. 5; SYNAPOMORPHY 37), and the close association of the ventralmost ray of the upper lobe of the caudal fin with the dorsalmost ray of the ventral lobe of that fin rather than the retention of the gap between those elements typical for characiforms (SYNAPOMORPHY 38). Further data on those characters and the conditions in those systems in outgroup taxa are found in Vari (1982a:5–9). Three other derived features of the caudal skeleton in Curimatopsis, the pronounced expansion of the penultimate principal caudal-fin ray of males (Curimatopsis SYNAPOMORPHY C), the possession of a second hypural free from PU_1 +U_1 but fused to the first hypural (Curimatopsis SYNAPOMORPHY D), and the contact in males of the third hypural with the fused first and second hypurals and the associated development posteriorly of interdigitations between those elements (Curimatopsis SYNAPOMORPHY E), were advanced as synapomorphies of the clade consisting of C. crypticus and C. evelynae. Curimatopsis myersi described subsequently (Vari, 1982b) has been found to also share these apomorphous features, and the more inclusive outgroup examinations associated with this study has confirmed the derived nature of the characters.

An additional synapomorphy in the caudal skeleton pertinent to hypotheses of subgeneric relationships in Curimatopsis has also been uncovered in this study. In males of C. evelynae, C. crypticus, and C. myersi, the posterior two free preural centra and the fused PU_1 + U_1 have distinct longitudinal dorsoventrally flattened lateral flanges arising from their midlateral surface. The processes evidently extend into the connective tissue layer between the epaxial and hypaxial musculature, and serve an an area of attachment for various ligamentous bands. Such processes on those posterior vertebrae are unknown elsewhere in the Curimatidae, nor have they been encountered in the examined outgroups. The lateral flanges on these posterior vertebral elements are thus hypothesized to be synapomorphies for Curimatopsis evelynae, C. crypticus, and C. meyersi (Curimatopsis SYNAPOMORPHY G).

A reduction to one set of uroneurals from the two sets typical for characiforms was hypothesized to be a synapomorphy for the species of Curimatopsis (Vari, 1982a:4, 5; SYNAPOMORPHY 40), a polarity congruent with the findings of this project. Further analysis has shown that a greatly reduced or absent set of second uroneurals is also characteristic of all species of Pseudocurimata. Within an examined series of six cleared and stained individuals of P. boulengeri, three were found to lack any indication of a second set of uroneurals and in the other three specimens there were present only very small bones on each side of the hypural complex in the region typically occupied by the second uroneurals. No indication was found of the second set of uroneurals in the examined cleared and stained specimens of P. peruanus or P. troscheli, and only a greatly reduced set of second uroneurals was found in the examined cleared individuals of P. lineopunctatus and P. patiae. This pronounced reduction or complete loss of the second set of uroneurals is hypothesized synapomorphous for the members of Pseudocurimata (SYNAPOMORPHY 103). That character is considered to be homoplasiously present in Curimatopsis within the context of the overall most parsimonious hypothesis of relationships within the Curimatidae.

LATEROSENSORY SYSTEM OF BODY

The vast majority of characiforms have a completely developed laterosensory canal system on the body with all lateral line scales having minimally a pore opening to the surface, and with some species and groups having more elaborate canal systems within the scales. A completely pored lateral line occurs in all members of the proximate outgroups to the Curimatidae, the families Prochilodontidae, Anostomidae, and Chilodontidae. Within the Curimatidae a completely pored laterosensory system on the body characterizes all members of the Curimatidae with the exception of the species of Curimatopsis and a subset of Cyphocharax species (saladensis, vanderi, punctata). Curimatopsis maulatus, described by Ahl (1934) as having an incompletely pored laterosensory canal system, is actually a juvenile of a Cyphocharax species in which that system is fully developed in the adults (pers. observ.). Although the reduction in this poring is hypothesized as derived given the fully developed laterosensory canal systems of the outgroups, the distribution of that character is not congruent with the final phylogeny of this study (Figure 44). The character is thus considered homoplasious at the generic level, with the reduced development of poring of the lateral line hypothesized synapomorphous for Curimatopsis species on the one hand (SYNAPOMORPHY 50) and the cited Cyphocharax species on the other.

A possible correlation exists between the reduced degree of poring of the laterosensory canal system of the body and the relatively small body size of many of the species with that character. Although paedomorphic features including a reduction in the degree of the development of the laterosensory canal system are often associated with relative miniaturization (Weitzman and Vari, 1988), the concept of such a direct correlation would appear at first to be qualified when applied to the Curimatidae since Curimatopsis microlepis, a species which achieves at least 90 mm SL, has an incompletely pored lateral-line. The concept of a miniature and the correlated suggestion of paedomorphosis is, nonetheless, applicable even to C. microlepis given the much larger body sizes of all members of the Prochilodontidae, the sister group to the Curimatidae, and proximate sister groups to Curimatopsis within the Curimatidae (see also discussion under “Convergent Characters”).

SQUAMATION

The species of the Curimatidae are characterized by complete squamation of the body, but without basal sheaths of scales on the dorsal or anal fin such as occur on the anal fin in the characid Markiana Eigenmann. Similarly the squamation on the caudal fin terminates only slighty posterior of the base of the caudal fin rays in the vast majority of the members of the Curimatidae. The one exception involves the species of Curimatella. Although juveniles of the genus have only a limited degree of squamation at the base of the caudal fin comparable to the situation in curimatid outgroups, there is an ontogenetic increase in the extent of squamation, with adults having scales over much of the proximate two-thirds of both lobes of the caudal fin.

The absence of such an extensive patch of scales on the caudal fin lobes, the condition in the remainder of the Curimatidae, is also characteristic of the Prochilodontidae and Chilodontidae, along with all genera of the Anostomidae other than for the few species of the genus Leporellus Lütken. Within the context of the overall phylogenetic hypothesis for the clade consisting of the Curimatidae, Prochilodontidae, Anostomidae, and Chilodontidae (Vari, 1983), the presence of caudal fin squamation in Curimatella is most simply considered synapomorphous for the members of the genus (SYNAPOMORPHY 104), albeit independently derived within the Anostomidae.

The relative size of body scales within the family Curimatidae as reflected in the number of scales along the lateral line from the supracleithrum to the base of the caudal fin demonstrates a nearly four fold range. That variation forms, however, a near continuum that makes it impossible to non-arbitrarily utilize much of that data for phylogenetic studies. Two exceptions involve the very high lateral-line counts for the species of Potamorhina, along with Cyphocharax abramoides. Vari (1984a:7) noted that the species of Potamorhina have 85–110 scales in that series, overlapping within the Curimatidae only with Cyphocharax abramoides (77–95 lateral line scales). The remainder of the family have 26 to 76 pored scales in a longitudinal series, and the Prochilodontidae, the sister group to the Curimatidae, typically has less that 80 lateral-line scales (R.M.C. Castro, pers. comm.). Thus the condition in Potamorhina is judged to be synapomorphous for the species of the genus (SYNAPOMORPHY 69) (see Vari, 1984a:7 for more details). The increased, although not as numerous, lateral line scales of Cyphocharax abramoides are considered to represent a homoplasious increase in that series.

Synapomorphy List and Phylogenetic Reconstruction

The previous section of the discussion details the numerous derived modifications of and within the Curimatidae over a variety of body systems that were discovered in the course of this and previous studies (Vari, 1982a, 1983, 1984a). Vari (1983:48) hypothesized that the Curimatidae and Prochilodontidae were sister groups, and that the Curimatidae (not including Anodus Spix and Eigenmannina Fowler) was a monophyletic assemblage. The anatomical studies associated with this project have uncovered additional information congruent with both of those hypotheses. The data from the examined body systems is also both relevant to a hypothesis of generic level relationships within that family, and to the evaluation of previously proposed genera.

In the following, shared derived characters congruent with a hypothesis of monophyly of the group consisting of the Prochilodontidae and Curimatidae will be discussed first. The majority of the characters supporting the hypothesis of the monophyly of that bifamilial lineage were analyzed and listed by Vari (1983) and all are noted again below. Some of these were not redescribed in detail in the preceeding sections of this paper, and the reader is referred to Vari (1983) for detailed information on those characters. Additional synapomorphies for the Curimatidae and Prochilodontidae were discussed in preceeding character descriptions, and are also listed below. The enumeration of the synapomorphies for the clade formed by those two families is followed by a listing and discussion of the less universal apomorphous states that characterize the Curimatidae, and the clades, named and unnamed, within that family.

FIGURE 44.—Cladogram of the most parsimonious hypothesis of phylogenetic relationships between the families Prochilodontidae and Curimatidae and within the Curimatidae (see Vari, 1983, for a discussion of synapomorphies for the Prochilodontidae). Numbered synapomorphies correspond to text.

A variety of alternative schemes have been proposed to convey phylogenetic information within a classification. A number of these systems involve the proposal of a name for each clade defined by shared derived characters, a method that would necessitate a number of taxa between the generic and familial levels in the Curimatidae. Formal nomenclatural recognition is given in this study only to the family and the major terminal sublineages recognized as genera. This simplified nomenclatural system is used since the recognition of taxa between the generic and familial levels for those subfamilial clades consisting of two or more genera would necessitate the proposal and utilization of at least four suprageneric taxa, a number that would increase if the terminal polychotomy were to be resolved by future studies. The resultant proliferation of suprageneric taxa within the family would do little to clarify the following discussion, or indeed might obfuscate the presentation. Although the proposed scheme of relationships cannot as a consequence be directly retrieved from the classification, that hypothesis is discussed in detail in the following section and is presented visually in Figure 44.

Characters pertinent to phylogenetic reconstructions at the subgeneric levels are not typically be discussed unless they represent homoplasies found at both the generic and/or suprageneric levels on the one hand, and at subgeneric levels on the other. Exceptions are made for those unique synapomorphies that are pertinent to the hypotheses of species level relationships advanced by Vari for Curimatopsis (1982a) and Potamorhina (1984a), and which are in some instances reiterated or even expanded in this study.

Subsequent to the reconstruction of the most parsimonious hypothesis of phylogenetic relationships among the genera within the Curimatidae, I discuss the distribution of homoplasious characters, those derived attributes with an incongruent distribution on the cladogram (Figure 44). The discussion deals with the two types of homoplasies indicated by the final phylogeny. The first class involves derived characters that are common to two subunits of the family which are not each other's closest relatives. The second group consists of evidently identical derived characters that occur both within a subunit of the Curimatidae and in some characiform outgroup. The discussion of the homoplasies in conjunction with the phylogenetic reconstruction provides the basis for the evaluation of the efficacy of previous classificatory schemes as indicators of the phylogenetic history of the components of the family, that is its suprageneric groupings and genera as recognized in this study. Convergent characters are also evaluated in terms of whether they represent innovative or reductive attributes, and relative to the degree of congruence in those attributes within subunits of the Curimatidae.

The most parsimonious hypothesis incorporating the previously described synapomorphies, including homoplasies, is presented in Figure 44. This hypothesis was first derived by manual construction. Its parsimony was confirmed by use of David L. Swofford's (1985) numeric computer algorithm PAUP (Phylogenetic Analysis Using Parsimony), version 2.4. Synapomorphies unique to lineages recognized as genera in this study were not included in the analysis except in the case of genera with components that shared derived features with another generic or suprageneric clade within the Curimatidae.

The data on 49 discretely variable polarized features with two to four character states was analyzed using the branch-andbound option of PAUP, guaranteed to find the most parsimonious trees. The analysis resulted in fifteen equally parsimonious trees with consistency indices of 0.825. These trees had identical topologies other than for the sequence of the genera Curimatella, Cyphocharax, Steindachnerina, and Pseudocurimata. Since those taxa form a terminal multichotomy, these fifteen trees are identical in terms of the phylogenetic hypothesis that they represent, and equivalent to the scheme of relationships in Figure 44. Characters are numbered sequentially from earlier to later dichotomies, simplifying the vizualization of character distribution, and allowing cross-referencinge of character descriptions and text discussions. The numbering of characters in the following text and in “Character Description and Analysis” corresponds to the numbered synapomorphies of Figure 44.

Characters pertinent to the species level phylogenetic reconstruction in Curimatopsis are sequentially identified alphabetically within the discussions of that genus and in Figure 45, but are not included in Figure 44. These form a separate character set.

MONOPHYLY OF THE CURIMATIDAE AND PROCHILODONTIDAE CLADE

Vari (1983:47) advanced eleven synapomorphies supporting the hypothesis that the Prochilodontidae is the sister group to the Curimatidae. These are listed below. Numbers 3, 9, 10, and 11 were discussed in detail by Vari (1983), to which the reader is referred for additional information. For the remaining synapomorphies, additional description and outgroup comparison may be found herein under “Character Description and Analysis.”

1.

Reorientation of the dorsal process of the fourth epibranchial anteriorly with its resultant extension over the dorsal surface of the fourth infrapharyngobranchial (Figures 5–13).

2.

Anterodorsal expansion of the cartilaginous fifth epibranchial, its attachment to the posterodorsal margin of the fourth epibranchial, and the resultant encirclement by those elements of the fifth efferent branchial artery (Figures 5, 6, 8–11).

3.

Large sac-like muscular epibranchial organ that extends dorsal to the medial elements of the dorsal portions of the gill arches (Vari, 1983:21–24).

4.

Conversion of the plesiomorphously flat fourth upper pharyngeal tooth plate into a curved ossification that is wrapped around the ventral, lateral, and medial surfaces of the fourth infrapharyngobranchial (Figures 5, 6, 8–16).

5.

Reduction or loss of dentition on the ventral surface of the fifth upper pharygneal tooth plate (Figures 5, 7–11).

6.

Reduction or loss of an ossified first basibranchial.

7.

Absence of dentition on the dorsal surface of the fifth ceratobranchial (Figures 25, 27).

8.

Anteromedially directed process on the ventral surface of the fourth ceratobranchial.

9.

Distinct posteroventrally aligned flange on the lateral surface of the opercle or a further derived condition of that process (Vari, 1983:29–30).

10.

Increase in the depth and width of the fossa for the scaphium resulting in the interconnections of the fossa with the lateral occipital foramen laterally, and the interior of the cranium anteriorly (Vari, 1983:38–41, fig. 34).

11.

Posterior development of the lateral margin of the exoccipital lateral to the foramen magnum, thereby forming a common aperture for the foramen magnum, cavum sinus imparis, and paired fossae for the scaphium. The exoccipital consequently forms a cover laterally for the the anterolateral surface of the scaphium (Vari, 1983:38–41, fig. 33).

The following additional derived characters shared by and uniting the Curimatidae and Prochilodontidae were discovered during this study. Additional description can be found under relevant sections of “Character Description and Analysis.”

12.

Constriction of the complex formed by the fourth infrapharyngobranchial and fourth upper pharyngeal tooth plate, resulting in a convex lateral margin to those-conjoined elements (Figures 15, 16).

13.

Expansion and restructuring of the uncinate process of the third epibranchial into an anterior process overlying the line of articulation between the third infrapharyngobranchial and third epibranchial (Figure 19).

14.

Subdivision of the anterior articular surface of the third epibranchial, with the expansion and reorientation of the medial portion of the articulation into a medially directed ossified process extending along a matching groove on the the anterodorsal portion of the fourth infrapharyngobranchial (Figures 5, 6, 8–11, 19).

15.

Expansion of the posterolateral portion of the third infrapharyngobranchial into a distinct dorsal flange (Figures 5, 6, 8–11).

As noted by Vari (1983:54–55) the phylogenetic hypothesis of a sister group relationship between the Curimatidae and Prochilodontidae agrees, partly or totally, with the classifications proposed by Günther (1864), Boulenger (1904), Regan (1911), Eigenmann (1917), Gregory and Conrad (1938), and Géry (1977b). All those authors included the majority of the taxa that are today considered to form the Curimatidae and Prochilodontidae in more encompassing groupings, along with taxa with which they are not closely related (Vari, 1983:54–55 for a more indepth discussion). Roberts (1973), in a significant shift from those earlier classifications, proposed that the relationships of the Prochilodontidae lies with the Anostomidae or the lineage formed by the Anostomidae and Chilodontidae rather than with the Curimatidae. Synapomorphies 12 to 15 discovered during this study, provide additional support for the hypothesis of the sister group relationship between the Curimatidae and Prochilodontidae. Those synapomorphies along with the shared derived characters proposed previously by Vari (1983) (SYNAPOMORPHIES 1–11) are incongruent with Roberts’ (1973) hypothesis of a closer phylogenetic association of the Prochilodontidae with the Anostomidae, or with the group formed by the Anostomidae and Childontidae rather than with the Curimatidae.

MONOPHYLY AND INTRAFAMILIAL RELATIONSHIPS OF THE FAMILY CURIMATIDAE

In a previous publication Vari (1983:48) noted that the Curimatidae was the least derived family among the taxa under discussion (Curimatidae, Prochilodontidae, Anostomidae, and Chilodontidae) in terms of number of synapomorphies (ten) found. The ten synapomorphies found in that study (Vari, 1983) for the Curimatidae are listed below. Of these, synapomorphies 17, 22, 24, and 25 were discussed in detail by Vari (1983) and are not further detailed within this paper. Additional discussion of the remaining synapomorphies may be found under “Character Description and Analysis.”

16.

Absence of dentition on the dentary and premaxilla.

17.

Possession of a third posttemporal fossa bordered solely by the epioccipital (Vari, 1983:37–38).

18.

Expansion of the anteroventral portion of the third hypobranchial into a vertical flange with anterior and posterior processes (Figures 23–24).

19.

Absence of an ossified first basibranchial (Figure 25).

20.

Posteroventral expansion of fifth upper pharyngeal tooth plate into curved, convoluted process (Figures 5, 7, 11).

21.

Secondary posterodorsal, cartilage capped process on the palatine which contacts a comparable process on the ventral wing of the lateral ethmoid (Figure 40).

22.

Cartilage-capped articular process along the ventral edge of the ventral wing of the lateral ethmoid that articulates with the palatine (Vari, 1983:26–27, fig. 25).

23.

Horizontal shelf on the medial surface of the metapterygoid.

24.

Large cartilaginous ethmoid block and widened mesethmoid (Vari, 1983, figs. 36, 37).

25.

Enlarged lagenar capsule (Vari, 1983:41).

Nine additional synapomorphies for the Curimatidae were discovered during this study (see also descriptions under “Character Description and Analysis”). They are as follows:

26.

Ventral ridge extending from posterior of anteroventral articular surface of fourth epibranchial along ventral surface of the main body of that element (Figure 5).

27.

Anterior reorientation of the primary axis of the dorsal process of the fourth epibranchial beyond the condition in the Prochilodontidae (Figures 5, 7–11).

28.

Longitudinal ridges on the dorsal surface of the fourth ceratobranchial (Figure 26).

29.

Dorsal convexity of the fifth ceratobranchial.

30.

Transverse expansion of the fifth ceratobranchial both medial and lateral of the line between the anterior and posterolateral cartilage bodies (Figure 27B,C).

31.

Presence of a well developed cord-like ligament running from the ventral hypohyal between the medial branchiostegal rays and extending along a groove on the midventral surface of the urohyal (Figure 32).

32.

Extension of the urohyal posteriorly beyond the point where the medial branchiostegal rays diverge laterally (secondarily shortened in Curimata and the clade consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (see discussion under “Hyoid Arch”)).

33.

Anterolateral expansion of the portions of the first to third branchiostegal rays proximate to the hyoid arch, and the resulting overlap of the articulation of the second branchiostegal with the anterior ceratohyal by the anterior portion of the third branchiostegal.

34.

Possession of a discrete ligamentous band, with a restricted area of attachment on the vomer, joining the neurocranium and the mesopterygoid.

As noted in the discussion of the “Opercular Aparatus,” the form of the opercle and subopercle may represent additional synapomorphies for the family, but were not included here due to problems with non-arbitrary quantification.

The genera Anodus and Eigenmannina have traditionally been placed in the Curimatidae (e.g., Fernández-Yépez, 1948) or associated in an unspecified manner with that family (e.g., Eigenmann, 1917) as a consequence of their common lack of jaw dentition. This character, unique to Anodus, Eigenmannina, and adults of the Curimatidae among characiforms, both New and Old World, was presumably the basis for the original description of three species of curimatids in Anodus (Anodus latior Spix = Potamorhina latior, Anodus ciliatus Müller and Troschel = Psectrogaster ciliata, and Anodus troschelii Günther = Pseudocurimata troschelii). Roberts (1974), in a significant shift, proposed that Anodus and Eigenmannina (considered congeneric by Roberts, 1974) were members of the Hemiodontidae, and not closely related to to Curimatidae. Subsequently, Géry (1977b:239) commented upon the overall similarity of hemiodontids, Anodus, and Eigenmannina, and noted Roberts’ (1974) publication in a footnote, but did not otherwise comment on the relationships of the different taxa. More recently, Géry (1984:357) has retained the “Anodins” (Anodus and Eigenmannina) in a broadly defined Curimatidae that does not form a monophyletic assemblage, and which he delimits from his “Hemiodins” (= Hemiodontidae). Although Géry (1984) noted that “The Anodins [Anodus and Eigenmannina] bear many resemblances to the Hemiodins,” he neither provided any reason for his rejection of Roberts’ (1974) hypothesis, nor did he elaborate on his continued alignment of Anodus and Eigenmannina with the Curimatidae.

The attributes listed by Roberts (1974:429) as justification for the inclusion of Anodus and Eigenmannina in the Hemiodontidae were an amalgam of three classes of characters. A number are synapomorphies for the Curimatidae (sensu stricto) (e.g., the cartilaginous articular surfaces between the palatine and the lateral ethmoid) that do define that family and serve to distinguish it from Anodus and Eigenmannina, but do not provide any insight into the phylogenetic position of those two genera to either the Curimatidae (sensu stricto) or the Hemiodontidae. The second group of features are shared primitive characters common to the Hemiodontidae, Anodus, and Eigenmannina (e.g., moderate coiling of the intestine), and which also occur in other groups of characiforms but are found in a derived condition in the Curimatidae. Such plesiomorphies are not useful in determining whether these three taxa form a monophyletic unit, or their possible phyletic associations with the Curimatidae. The third class of characters are shared derived modifications common to the Hemiodontidae, Anodus, and Eigenmannina, but which are not typical of the Curimatidae. Characters of that class cited by Roberts (1974) include the increased number of vertebrae, and the fusion of the first and second hypurals into a single ossification autogenous from the remainder of the hypural fan. Such characters are appropriately used as indicators of relationship and support Roberts’ (1974) hypothesis that Anodus and Eigenmannina are aligned with the Hemiodontidae.

A more indepth evaluation of the placement of Anodus and Eigenmannina within the Hemiodontidae and a more rigorous definition of that family based on shared derived characters are both outside the scope of this study. The results of this study are, however, congruent with the hypothesis that Anodus and Eigenmannina are not closely related to the Curimatidae. Those genera share the synapomorphies noted above indicating that they are aligned phyletically with the Hemiodontidae. Furthermore those two genera lack the vast majority of the numerous hypothesized synapomorphies for the clade consisting of the Prochilodontidae and Curimatidae (SYNAPOMORPHIES 1–15), and the shared derived characters that delimit the Curimatidae (SYNAPOMORPHIES 16–34). The continued retention of Anodus and Eigenmannina in the Curimatidae would consequently require a hypothesis of secondary loss of nearly all of the derived characters in those two genera. That factor in combination with some of the characters cited by Roberts (1974) (see paragraph above) refute the implicit hypothesis of a close phyletic relationship of Anodus and Eigenmannina with the Curimatidae as advanced by Géry (1984).

The scheme of hypothesized phylogenetic relationships within the Curimatidae (Figure 44) has a basal pinnate form. The first dichotomy is between the clade consisting of the five species of Curimatopsis and the lineage formed by Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

Curimatopsis

Vari (1982a), in a revisionary study of Curimatopsis, advanced eight synapomorphies that served to delimit the four then-known species in the genus. These shared derived characters are also common to an additional species, C. myersi, that was described subsequently (Vari, 1982b). The five species of Curimatopsis occur in the Orinoco, Amazonas, and Paraguay rivers, and in some rivers of the Atlantic slopes of the Guyanas (see Vari, 1982a,b for details on those distributions). The derived characters advanced as synapomorphies for Curimatopsis by Vari (1982a) are as follows:

35.

Expansion of the neural and haemal spines of the two posterior free preural centra into transversely flattened plates in the males.

36.

Presence of basal spurs on the middle caudal-fin rays in the males.

37.

Expansion of the penultimate principal caudal-fin ray of the lower lobe of the caudal fin in the males.

38.

Ventral reorientation of the ventralmost ray of the upper caudal fin lobe.

39.

Ventral expansion of the metapterygoid and the consequent reduction in the relative size of the metapterygoid-quadrate fenestra (Figure 42A).

40.

Reduction to a single pair of uroneurals.

41.

Absence of an ossified antorbital.

42.

Reduction in the relative sizes of the supraorbital and the sixth infraorbital (dermosphenotic).

These synapomorphies are here supplemented by additional derived characters that also delimit the clade formed by the five species of Curimatopsis including C. myersi:

43.

Oblique angle of articulation between the third infrapharyngobranchial and third epibranchial (Figure 15).

44.

Very oblique angle of articulation between the second infrapharyngobranchial and second epibranchial, and the associated expansion of the second infrapharyngobranchial posterolaterally (Figure 15).

45.

Possession of narrow rather than broad flanges along the ventrolateral margins of the urohyal.

46.

Lack of a laterosensory canal segment in the first infraorbital.

47.

Restructuring of the premaxilla into a very slender ossification.

48.

Enlarged paddle-shaped body of the maxilla (Figure 38A).

49.

Reduction of the ethmo-palatine cartilage to a relatively small body at the tip of the premaxilla (Figure 40A).

50.

Reduction in the degree of scale poring of the laterosensory canal system of the body.

An additional possible synapomorphy for the members of Curimatopsis is the relatively elongate urohyal extending distinctly beyond the point of lateral divergence of the branchiostegal rays (see discussion under “Hyoid Arch”).

Vari (1982a:10) proposed a phylogenetic scheme for the four species of Curimatopsis recognized in that study. As mentioned previously, an additional species (C. myersi) from the Río Paraguay basin was discovered and subsequently described (Vari, 1982b). The phylogenetic scheme for the expanded Curimatopsis is presented in Figure 45. Vari (1982a) discussed the following synapomorphies shared by Curimatopsis macrolepis and C. microlepis:

A.

Lengthening of the postorbital portion of the head.

B.

Terminal, upturned mouth with the lower jaw overlapping the anterior margin of the upper.

FIGURE 45.—Cladogram of the most parsimonious hypothesis of relationships within the genus Curimatopsis. Numbered and lettered synapomorphies correspond to text.

During the course of this analysis those two synapomorphies have been supplemented by an additional character that was not discussed by Vari (1982a):

C.

Expansion of the anteroventral portion of the posttemporal and the lengthening of the segment of the laterosensory canal associated with the region of the bone.

The anteroventral region of the posttemporal is relatively small and has a short laterosensory canal segment in the Prochilodontidae, other species of Curimatopsis, and other genera of the Curimatidae. Given the unique nature of the expansion of that region of the bone in C. microlepis and C. macrolepis among curimatids, that correlation is hypothesized to be a synapomorphy for those two species. Similarly the elongation of the associated laterosensory canal segment in that region of the posttemporal is also hypothesized as synapomorphous for those species (SYNAPOMORPHY C).

The clade consisting of Curimatopsis evelynae, C. crypticus, and C. myersi is defined by three characters previously proposed by Vari (1982a):

D.

Pronounced expansion of the penultimate principal ray of the lower lobe of the caudal fin in males.

E.

Possession of a hypural 2 that is separate from the fused PU_1 + U_1, but fused to hypural 1.

F.

Contact in the males of hypural 3 with the fused hypural 1 and 2, and the development posteriorly of interdigitations between those elements.

Additional synapomorphies for that clade are as follows:

G.

Absence of an ossified sixth infraorbital (I0_6).

H.

Laterally expanded longitudinal flanges on the midlateral surface of the posterior two free preural centra and the fused PU_1 + U_1.

Autapomorphies for Curimatopsis evelynae discovered since Vari (1982a) are primarily reductive, and given the small adult body size of the species may be the consequence of a paedomorphic process. These characters, which were not discussed by Vari (1982a), are as follows:

I.

Reduction in the degree of ossification of the laterosensory canals in the second infraorbital.

J.

Reduction in the degree of ossification of the laterosensory canals in the fourth infraorbital.

K.

Absence of an ossified suprapreopercle.

Ossified laterosensory canal segments in the second and fourth infraorbitals and the ossification of the laterosensory canal above the preopercle as a separate supraperopercle are generalized for all other curimatids. Synapomorphies I, J, and K are consequently considered autapomorphous for C. evelynae.

Autapomorphies for the remaining Curimatopsis species have not been discovered, nor have characters been discovered that allow us to advance a hypothesis of sister species relationships within the trichotomy formed by C. evelynae, C. crypticus, and C. myersi.

Potamorhina, Curimata, Psectrogaster, Steindachnerina,

Pseudocurimata, Curimatella, and Cyphocharax

These genera form a clade defined by thirteen synapomorphies:

51.

Medial bony spur extending posteroventrally from the medial surface of the main body of the fourth epibranchial.

52.

Pronounced anterior reorientation of the dorsal process of the fourth epibranchial beyond the condition in either the Prochilodontidae or Curimatopsis (Figures 7–11).

53.

Anterior bony spur extending forward from the main body of the fourth epibranchial. That process serves as the area of attachment for the ligament extending between the third and fourth epibranchials (Figures 8, 10, 11, 13, 14).

54.

Posterior lengthening of the fifth upper pharyngeal tooth plate, and the reduction of the dentition associated with that ossification (Figures 6–11).

55.

Transversely subdivided posterior articular cartilage on the third infrapharyngobranchial (Figures 8, 10, 11).

56.

Reduction or elimination of the gap between the articular cartilages on the anterior margin of the second hypobranchial (Figure 22B–D).

57.

Enlarged ventral process on the fourth ceratobranchial that serves as a point of attachment for ligamentous tissues associated with the ventral aorta (present in Potamorhina, Curimata, and Psectrogaster, secondarily lost (SYNAPOMORPHY 93, below) in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax).

58.

Expansion of the portion of the ligamentum primordiale proximate to the A_1 portion of the Adductor Mandibulae muscle, either with or without an included cartilage body.

59.

Opposing articular facets on the premaxilla and maxilla at their points of contact.

60.

Expanded posterodorsal process of the main body of the maxilla (Figure 38B).

61.

Sigmoid dorsal margin of the dentary (Figure 39B).

62.

Subdivision of the articular cartilage of the palatine into an anterior portion contacting the ethmopalatine cartilage and vomer, and a posterior section with a dorsal articular surface that contacts the ventral articular process of the lateral ethmoid (Figure 40B).

63.

Band-like ligament between the neurocranium and suspensorium with a discrete area of attachment to both the vomer and the mesopterygoid.

The large number of synapomorphies for this clade represent major restructurings of the gill arches, jaws, and associated soft tissues relative to the state of those systems in Curimatopsis. These perhaps reflect the increased specialization for a microphagous diet in the species of Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. These modifications involve a number of systems which undergo further modifications at less inclusive levels of universality within the family. These independent evolutionary histories lead me to deal with these synapomorphies as thirteen independent features rather than attempting to arbitrarily group them as a reduced number of composite characters.

The lineage defined by characters 51–63 is, in turn, divisible into two monophyletic groups: one consisting of the species of the genus Potamorhina, the other formed by the genera Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

Potamorhina

The genus Potamorhina consists of five relatively large-bodied species. Potamorhina laticeps is limited to the Lago Maracaibo basin. P. squamoralevis inhabits the Río Paraguay basin. Potamorhina latior and P. pristigaster are endemic to the Río Amazonas system. P. altamazonica is common to the Río Amazonas system and the Río Orinoco (see Vari, 1984a, for further details on species distribution). Potamorhina was defined by Vari (1984a: 13) on the basis of six synapomorphies, listed below. Synapomorphy 68 was described in detail by Vari (1984a) and is not discussed elsewhere in this paper. The remainder are described herein under “Character Description and Analysis”:

64.

Horizontal lengthening of the anterodorsally aligned dorsal process of the fourth epibranchial and its associated distal cartilage (Figure 10).

65.

Contact of the distal cartilage of the fourth epibranchial with the cartilage of the uncinate process of the third epibranchial (Figure 10).

66.

Horizontal elongation of the fourth basibranchial, fourth ceratobranchial and the complex formed by the fourth infrapharyngobranchial and fourth upper pharyngeal tooth plate (Figure 10).

67.

Elaboration of the laterosensory canal system in the sixth infraorbital from a tripartite system into one with four or more branches (Figure 36c).

68.

Presence of two or three unbranched rays and 11–16 branched rays in the anal fin (Vari, 1984a:7).

69.

Possession of 85–110 pored lateral line scales from the supracleithrum to the hypural joint.

The additional synapomorphies for the species of Potamorhina discovered during this study are as follows:

70.

Lengthening of the fifth epibranchial into a long anteriorly tapering body (Figure 10).

71.

Subdivision of the articular process on the uncinate process of the first epibranchial (Figure 21).

72.

Posterior elongation of infraorbitals four and five (I0_4 and I0_5) and the associated lengthening of the posterior horizontal laterosensory canal segment in the fourth infraorbital.

73.

Greater posterior development and more oblique orientation of the opercle.

74.

Posterior development of the interopercle into a large triangular plate between the preopercle, subopercle, and opercle.

An additional possible synapomorphy for the members of Potamorhina is the relatively elongate urohyal extending distinctly beyond the point of lateral divergence of the branchiostegal rays (see discussion under “Hyoid Arch”).

Vari (1984a: 13) advanced a hypothesis of relationships among the five recognized species of Potamorhina. Only one additional character pertinent to that hypothesis was uncovered during this study and it is congruent with the previously proposed phylogenetic scheme for and within Potamorhina, (see Vari, 1984a:4–11, fig. 6).

The additional derived character discovered during this study is an autapomorphy for Potamorhina pristigaster. This feature involves the marked shift posteriorly of the fourth and fifth infraorbitals and the consequent more acute angle between the axes of the laterosensory canal segments of those elements. As discussed previously, this shift is somewhat similar in overall appearence to that in species of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (SYNAPOMORPHY 95). The morphological plan of these elements in Potamorhina pristigaster is a consequence of a posterior shift in the position of the elements relative to the orbit, and differs in various details from the condition in the cited genera. In light of those differences and within the context of the overall most parsimonious hypothesis of relationships, the state in P. pristigaster is considered non-homologous with that in Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

Curimata, Psectrogaster, Steindachnerina,

Pseudocurimata, Curimatella, and Cyphocharax

The sister lineage to Potamorhina is a clade consisting of six genera: Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. That lineage is delimited by three shared derived characters:

75.

Elimination of the gap between the anterior articular cartilages along the anterior margin of the second hypobranchial with the fusion of the cartilage bodies into a single mass (Figure 22C–D).

76.

Development of a buccopharyngeal complex consisting of three longitudinal fleshy folds on the roof of the oral cavity, or a further derived elaboration of that complex.

77.

Well developed ridge on the medial surface of the metapterygoid (Figures 41, 42).

The clade delimited by synapomorphies 75–77 contains two subunits defined by less universal derived characters. These are Curimata on the one hand, and the clade consisting of Psectrogaster, Steindachnerina, Curimatella, and Cypocharax on the other.

Curimata

The genus Curimata is a distinctive group of moderate to large sized species inhabiting the Rí Magdalena, the Rí Orinoco, the rivers of the Atlantic slopes of the Guyanas, some of the rivers of northeastern Brazil, and the Amazon basin. Curimata is characterized by six synapomorphies:

78.

Ontogenetic reconfiguration of the medial spur on the fourth epibranchial into a ventrally expanded process contacting the medial margins of the fifth upper pharyngeal tooth plate (Figures 7, 8).

79.

Development of a median shelf on the dorsal margin of the spur of the fourth epibranchial, and the associated pronounced fenestration of that spur (Figure 8).

80.

Medial shift of the medial spur and ventral articular processes of the fourth epibranchial, and of the associated fifth upper pharyngeal tooth plate (Figure 14).

81.

Reduction or loss of the first infrapharyngobranchial.

82.

Elaboration of the three primary folds of the buccopharyngeal complex into large ventral flaps, and the development of numerous secondary parallel folds on the roof of the buccal cavity (Figure 28).

83.

Thickened anteromedial portion of the metapterygoid (Figure 42D).

An additional possible synapomorphy for the members of Curimata is the relatively short urohyal extending only to the point of lateral divergence of the branchiostegal rays. The morphology of that system may represent a secondary reversal from the condition in a more inclusive clade (see discussion under “Hyoid Arch”).

Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax

These genera, comprising the sister group to Curimata, share two derived characters:

84.

Possession of a discrete cartilage embedded in an aponeurotic covering within the expanded basal portion of the ligamentum primordiale (Figure 37).

85.

Posteroventral expansion of the mesopterygoid into an elongate process extending into and partially or totally subdividing the metapterygoid-quadrate fenestra (Figure 41B).

Synapomorphies 84 and 85 unite two clades: that recognized herein as Psectrogaster, and the lineage consisting of Steindachnerina, Curimatella, Pseudocurimata, and Cyphocharax.

Psectrogaster

The species of Psectrogaster are distributed within the Rí Orinoco, Essequibo River, Amazon basin, some of the rivers of northeastern Brazil, and the Rí Paraguay system. Psectrogaster species have in common the following seven synapomorphies:

86.

Posterior elongation of the medial spur on the main body of the fourth epibranchial (Figure 9).

87.

Elongation and distal twisting of the fifth upper pharyngeal tooth plate (Figure 9).

88.

Well developed longitudinal ridge on the ventral surface of the third epibranchial.

89.

Well developed longitudinal ridge on the ventral surface of the second epibranchial.

90.

Distinct flange on the dorsal surface of the second infrapharyngobranchial that overlies the anteromedial portion of the third infrapharyngobranchial.

91.

Distinct longitudinal ridge on the ventral surface of the first epibranchial.

92.

Longitudinal ridge on the dorsal surface of the third ceratobranchial.

An additional possible synapomorphy for the members of Psectrogaster is the relatively elongate urohyal extending distinctly beyond the point of lateral divergence of the branchiostegal rays (see discussion under “Hyoid Arch”).

Steindachnerina, Pseudocurimata, Curimatella,

and Cyphocharax

The lineage consisting of these genera is characterized by four synapomorphies:

93.

Secondary loss of the enlarged ventral process on the fourth ceratobranchial that is found in Potamorhina, Curimata, and Psectrogaster (SYNAPOMORPHY 57).

94.

Presence of a basihyal tooth plate.

95.

Reorientation of the canals in the fourth and fifth infraorbitals (IO_4 and IO_5) with the consequent reduction in the angle of the primary axes between the laterosensory canal segments in those ossifications (Figure 35c).

96.

Reduction of the laterosensory canal system in the sixth infraorbital (IO_6) to a single tube extending between the fifth infraorbital and pterotic laterosensory canal segments (Figure 36D).

An additional character possibly synapomorphous for the lineage consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax involves the form of the urohyal. These genera are characterized by a relatively short urohyal that reaches posteriorly to the point of lateral divergence of the branchiostegal rays. Three alternative, equally parsimonious, hypotheses exist to explain the occurrence of the derived condition, the more elongate urohyal, in Curimatopsis, Potamorhina, and Curimatella, One of these alternatives involves the derived secondary reduction of the urohyal in the clade consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax (the other alternatives are discussed under “Hyoid Arch”).

It is not possible to resolve the hypothesis of relationships among the remaining genera in the family (Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax) on the basis of the characters uncovered during this study. Synapomorphous characters do, however, permit the definition of three of these groups (Steindachnerina, Pseudocurimata, and Curimatella) as individual monophyletic units. The remaining genus, Cyphocharax, is not delimited by any known derived characters, and it is thus possible that some or all of its component taxa may actually be more closely related to Steindachnerina, Pseudocurimata, or Curimatella, or some combination of these genera than to the remaining species of Cyphocharax (see also discussion of Cyphocharax, below). These four remaining recognized genera are discussed sequentially, with the order of presentation not indicative of any underlying hypothesis of relationships.

Steindachnerina

Steindachnerina is the largest genus in the Curimatidae, with a geographic distribution covering much of the known range of the family in South America east of the Andes together with a single species (S. atratoensis) to the west of the Andean Cordilleras in the Río Atrato system of Colombia. The hypothesized synapomorphies for the species of Steindachnerina are as follows:

97.

Ventral and dorsal ridges on the lateral surface of the second infrapharyngobranchial that bracket the anteromedial portion of the third infrapharyngobranchial.

98.

Expansion of the cartilaginous portion of the first infrapharyngobranchial and its contact with the second infrapharyngobranchial.

99.

Attachment of the ligament between the second and third hypobranchials to a distinct anterior process on the anterolateral surface of the ventral process of the third hypobranchial (Figure 24).

100.

Lateral expansion of the anterior portion of the basihyal and associated basihyal tooth plate (Figure 33B).

Pseudocurimata

The species of Pseudocurimata are limited to the trans-Andean drainages of northwestern South America from the Río Atrato of Colombia to the Río Chira of northern Peru. This distribution is nearly totally allopatric to the remainder of the family other than for the partial overlap of the range of P. lineopunctata with that of Steindachnerina atratoensis in the Río Atrato system. Synapomorphies for the genus are as follows:

101.

Expansion of the portion of the second hypobranchial proximate to the third basibranchial and the fission of the articular cartilage on the anterior and medial surfaces of the second hypobranchial (Figure 22D).

102.

Posterior shift of the point of interdigitation of the first proximal pterygiophore of the dorsal fin to between the fifth and sixth, or sixth and seventh, neural spines (Figure43B–C).

103.

Pronounced reduction or complete loss of the second set of uroneurals.

Curimatella

The relatively few species (probably six or seven) of Curimatella occur in the ríos Orinoco, Amazonas, Essequibo, Sào Francisco, and the La Plata basin. The genus is distinguished by the presence of the following synapomorphy:

104.

Layer of scales extending across the lobes of the caudal fin.

Cyphocharax

Taxa assigned to Cyphocharax in this study are widely distributed through nearly the entire range of the family Curimatidae with the exception of the trans-Andean rivers to the west and south of the Río Magdalena of Colombia that are inhabited by species of Pseudocurimata. Cyphocharax species are also absent in the rivers of northeastern Brazil.

The characters discovered during this study have not included any synapomorphies congruent with a hypothesis of the monophyly of Cyphocharax. The combination of that lack of any defining characters for Cyphocharax and the multichotomy that exists between that genus, Curimatella, Pseudocurimata, and Steindachnerina leaves open the possibility that some components of Cyphocharax may be more closely related to one or more of the other genera in the multichotomy than to the remaining species of Cyphocharax.

Although Cyphocharax is not readily definable on the basis of derived characters, there are some recognizable assemblages within that genus that are to varying degrees phyletically and phenetically distinguishable and may represent monophyletic subunits of the genus. The largest of these involves eleven nominal taxa characterized by a distinctive dark midlateral spot on the caudal peduncle, such as is typical for Cyphocharax spilurus. Other nominal taxa of the C. spilurus species group sharing this evidently derived character are C. spiluropsis, C. gillii, C. surinamensis, C. helleri, C. stigmaturus, C. esperanzae, C. ucayalensis, C. vandellii, C. esperanzae pijpersi, and C. spilota (see Table 2 for information on authors and original generic placement of these taxa).

A second assemblage consists of curimatids of relatively small adult body size, the first described being C. saladensis. The C. saladensis species group consists of that species, C. punctata, and C. vanderi all of which share a reduction in the extent of the poring in the lateral line, a less developed laterosensory canal system of the head, in particular of the canal segments in the infraorbitals, and a general reduction in the degree of development of various cranial sculpturing. These paedomorphic characters cannot be evaluated here as to the particular heterochronic process that has resulted in these results, but are potentially derived characters that unite these species into a monophyletic group (see Weitzman and Vari, 1988, for further discussion of reductive characters and of their utility in phylogenetic reconstructions).

Another major assemblage, the Cyphocarex gilberti species group, includes species sharing overall distinctive pigmentation patterns, including a rhomboidal caudal pigmentation pattern in juveniles and random body spotting, which are possibly derived. The nominal members of the C. gilberti species group are C. gilberti, C. voga, C. albula, C. grandocule, C. santacatarinae, and C. modesta (see Table 2 for authors and original generic assignments). Cyphocharax platana and C. nagellii, in turn, are phenetically very similar species with distinctive body forms and having contiguous ranges in the La Plata and upper Río Paraná systems respectively. These may be sister species. Groupings among the remaining nominal Cyphocharax species are not as apparent at this time.

Cyphocharax Fowler (1906) as utilized in this study is considered to have four synonyms: Xyrocharax Fowler (1913b), Hemicurimata Myers (1929), Curimatoides Fowler (1940), and Cruxentina Fernández-Yépez (1948). Cyphocharax, Xyrocharax, Hemicurimata, and Curimatoides all have type species which either represent the same species or very closely related species, all of which belong to the C. spilurus species group. Xyrocharax has not been utilized by authors other than Fowler (1913b), whereas Curimatoides is evidently based on a single aberrant individual lacking an adipose dorsal fin.

Given the lack of resolution of the phylogeny at this point and the clumping of the vast majority of the type species of the available nominal genera in a small subunit of this assemblage it is most conservative to recognize a single genus for this questionably monophyletic assemblage. The alternative, the recognition of all nominal available genera, or an intermediate number of taxa would necessitate the creation of a series of new genera for the different species groupings described above for which generic names have not been previously proposed. Such an elaboration of the supraspecific taxonomy within this assemblage is considered inappropriate given the phylogenetic uncertainties involving interrelationships among the species united within Cyphocharax at this time, and in light of the absence of any advantages to such a more complex taxonomic scheme.

Unassigned

One feature, involving the elongation of the urohyal, was assigned a synapomorphy number for inclusion in the PAUP analysis and for discussion purposes (see “Urohyal” and “Convergent Characters”), but does not appear on the cladogram (Figure 44). The reason is that three interpretations of its behavior on the cladogram, each involving three independent derivations or losses, are equally parsimonious. The feature is as follows:

105.

Elongation of the urohyal past the point of lateral divergence of the branchiostegal rays in Curimatopsis, Potamorhina, and Psectrogaster.

Convergent Characters

The hypothesis of phylogenetic relationships within the family Curimatidae proposed in this study is the most parsimonious derivable from those characters showing discrete variability within the family when considered in the context of the available information on character homology, polarity, and distribution. The utilization of the principle of simplicity (parismony), as the criterion to evaluate the preferability of alternative hypotheses has been the subject of some controversy (e.g., Felsenstein and Sober, 1986). However, this procedure, the acceptance of the hypothesis that requires the fewest ad hoc assumptions, is still preferable (Beatty and Fink, 1979; Eldredge and Cracraft, 1980; Wiley, 1981). I recognize, nonetheless, that evolutionary processes are not necessarily parsimonious, with the result that evident homoplasies are features of most phylogenetic schemes including the one proposed in this study.

The hypothesis of phylogenetic relationships described herein includes features, from diverse body systems, that have a phyletic distribution incongruent with the final most parsimonious phylogenetic scheme. Such incongruent derived characters, homoplasies, will be evaluated here within two contexts. The first framework deals solely with the phylogenetic distribution of the characters regardless of the type of character involved. Do the homoplasies under consideration characterize two or more independent sublineages within the Curimatidae (convergences internal to the Curimatidae), or do they represent the independent acquisition of the character in question both in a subunit of the Curimatidae and in some characiform outgroup (convergences external to the Curimatidae)? Those comparisons serve to emphasize the phyletic patterns of homoplasy and focus attention on those clades that evidently have independently undergone congruent patterns of convergent evolution. Admittedly the distinction between internal and external homoplasies is based on arbitrary taxonomic limits, but serves nonetheless to convey a general sense of the phyletic proximity of the clades involved in the comparisons.

One can alternatively discuss homoplasies in terms of their innovative or reductive natures (Weitzman and Fink, 1985) outside of a strictly phyletic context. Innovative characters, having “additional features beyond those present in the outgroups” (Weitzman and Fink, 1985:10), are a consequence of changes in peramorphic processes and most commonly represent terminal additions in overall developmental sequences. Reductive characters in contradistinction involve the reduction or loss of a feature present in the outgroups and may result from a number of different paedomorphic developmental changes resulting from progenesis, neoteny, and post-displacement. The analysis of common patterns of reductive homoplasies within a phylogentic scheme derived from multiple characters, innovative and reductive, congruent and incongruent, permits an evaluation of the utility of at least some reductive characters as indicators of phylogenetic relationship.

Since the homoplasies to be discussed within these two contexts (phyletic, and innovative versus reductive) are the same, they will only be detailed in the first set of discussions, those on phyletic distribution. Homoplasies in that discussion are divided between internal homoplasies and external homoplasies, and are listed sequentially by synapomorphy number. These synapomorphies will also be discussed in the context of reductive versus innovative homoplasies.

The homoplasies found in two or more subunits of the Curimatidae (internal homoplasies) and their phylogenetic distributions are as follows, listed by synapomorphy number (see also “Character Description and Analysis” and “Synapomorphy List and Phylogenetic Reconstruction”):

21.

Subdivided articular processes on the uncinate process of the first epibranchial in Potamorhina and the lineage consisting of Curimata incompta, C. cyprinoides, C. copei, C. schomburgkii, C. edentulus, C. planirostris, C. kneri, C. mivartii, C. cerasina, C. aspera, C. simulata, C. cisandina, C. alleni, and two undescribed species of Curimata.

28.

Elaboration of the buccopharyngeal complex in Curimata species and the majority of Steindachnerina species.

46.

Absence of a laterosensory canal segment in the first infraorbital in all Curimatopsis species, Steindachnerina binotata, Cyphocharax gillii, C. saladensis, C. punctata, and C. vanderi. This reduction also occurs in various characiform outgroups but not in the proximate outgroups Prochilodontidae, Anostomidae, and Chilodontidae.

50.

Reduction in the degree of poring of the laterosensory canal system on the body in Curimatopsis and in three species of Cyphocharax (vanderi, punctata, and saladensis); also reduced in some other characiforms, but not in the proximate outgroups to the Curimatidae.

69.

High number of lateral-line scales in Cyphocharax abramoides and in the species of Potamorhina.

88.

Well developed ventral longitudinal ridges along the ventral surface of the third epibranchial in Curimata aspera, C. simulata, C. cerasina, and all Psectrogaster species.

89.

Well developed ventral longitudinal ridges along the ventral surface of the second epibranchial in Curimata mivartii, C. aspera, C. simulata, C. cerasina, C. cisandina, C. alleni, two undescribed Curimata species, and all species of Psectrogaster.

90.

Distinct flange on the anterodorsal surface of the second infrapharyngobranchial in Psectrogaster (see also discussion of Synapomorphy 97 and under “Third Epibranchial”).

91.

Longitudinal ridge along the ventral surface of the first epibranchial in Psectrogaster and in two species of Curimata.

92.

Longitudinal ridge along the dorsal surface of the third ceratobranchial in Psectrogaster and in Curimata mivartii, C. aspera, C. simulata, C. cerasina, C. alleni, and two undescribed species of Curimata.

94.

Presence of a basihyal tooth plate in a subset of species of Curimata and in the vast majority of the species in the lineage consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax.

97.

Distinct flange on the anterodorsal surface of the second infrapharyngobranchial in Steindachnerina (see also 91, above, and discussion under “Third Epibranchial”).

102.

Posterior position of the interdigitation of the first proximal pterygiophore of the dorsal fin with the proximate neural spines in Curimata ocellata, C. semitaenitata, and all Pseudocurimata species (also present in some outgroups, see “Supraneurals”).

105.

Elongation of the urohyal past the point of lateral divergence of the branchiostegal rays in Curimatopsis, Potamorhina, and Psectrogaster. Three alternative, equally parsimonious hypothesis exist (see discussion under ‘Urohyal’). The first is that a lengthened urohyal is synapomorphous for all species of the Curimatidae and is secondarily independently shortened in Curimata and the lineage consisting of Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax. The elongation may also be acquired at the level of the Curimatidae, with a reduction in the clade consisting of Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, Curimatella, and Cyphocharax, with a secondary lengthening in Psectrogaster. Finally, the elongation may have been independently acquired within each of the three lineages, Curimatopsis, Potamorhina, and Psectrogaster. The feature was not used in the cladogram because of the several possible interpretations of its distribution.

As can be seen in the above listing, a number of generic and subgeneric subunits possess characters homoplasious relative to the overall most parsimonious hypothesis of intrafamilial relationships. Nonetheless, relatively few patterns of repeated homoplasy among those taxa were discovered during the course of this study. Reductive features of the laterosensory canal system of the head and body are common to Curimatopsis species and a subunit of Cyphocharax (SYNAPOMORPHIES 46 and 50, see also discussion in next section). Psectrogaster and subunits of Curimata of varying levels of inclusiveness also share several convergences involving longitudinal ridges on various gill arch elements (SYNAPOMORPHIES 89, 92 at one level, and 89, 91 at another). The differing levels of inclusiveness at which these convergences are common in those genera, along with overall parsimony considerations indicate that these are homoplasious rather than homologous features.

The second subset of homoplasies are derived synapomorphies occurring in a subunit of the Curimatidae and also in a characiform outgroup (external homoplasies). These are as follows:

16.

Absence of jaw teeth in all members of the Curimatidae, and in Anodus and Eigenmannina of the Hemiodontidae.

39.

Reduction in the size of the metapterygoid-quadrate fenestra as a consequence of the ventral expansion of the metapterygoid in Curimatopsis, and in the Chilodontidae.

41.

Absence of an ossified antorbital in Curimatopsis in the Curimatidae, and in the African characid Lepidarchus adonis.

100.

Expansion of the basihyal and basihyal tooth plate in Steindachnerina, and in the Prochilodontidae.

104.

Sheet of scales across the lobes of the caudal fin in Curimatella, and in the genus Leporellus in the Anostomidae.

Synapomorphies 46, 50, and 102, homoplasious within the Curimatidae, are also synapomorphous for some lineages outside of that family. Only synapomorphy 102 is homoplasiously present in proximate outgroups of the Curimatidae.

The above listing of external homoplasies should not be considered exhaustive since it is not feasible to carry out outgroup comparisons against the entire spectrum of characiform outgroups. These comparisons have for practicality been focused on the proximate sister groups to the Curimatidae, the Prochilodontidae, Anostomidae, and Chilodontidae.

An alternative way to look at the above attributes is to ask whether they are innovative or reductive, and whether these classes of homoplasies demonstrate a meaningful pattern relative to the arrived at phylogenetic hypothesis. The innovative characters in the previous listings having a homoplasious distribution internal to the Curimatidae are numbers 28, 69, 88–92, 94, 102, and 105. The innovative characters in the previous listing having a homoplasious distribution external to the Curimatidae are 39, 100, and 104.

The innovative homoplasies are common to some members of the Curimatidae and a diversity of outgroups. These do not, however, demonstrate any patterns that would support alternative hypotheses of relationships. This lack of congruence makes it unfruitful to speculate on common underlying factors resulting in these homoplasies.

The reductive homoplasies, internal to the Curimatidae, uncovered during this study are synapomorphies 46 and 50. Those external to the Curimatidae are synapomorphies 16 and 41.

Reductive characters and their utility in phylogenetic reconstructions in fishes in general and characiforms in particular have been the subject of discussions by various authors (e.g., Weitzman and Fink, 1983; Weitzman and Vari, 1988). As noted by those authors, paedomorphic features cannot be a priori distinguished from primitive states in the absence of information on phylogenetic relationships derived from multple character systems involving innovative and reductive apomorphies. The bulk of the characters used by different authors in advancing hypotheses of relationships in characiforms involve external characters. In the Curimatidae the external reductive features most often used for those purposes have involved the extent of development of the laterosensory canal system, in particular the degree of scale poring associated with the lateral line on the body.

The use of a reduction in the degree of poring on the lateral line to distinguish a species at the supraspecific level within the Curimatidae was first advanced by Steindachner (1876) who proposed Curimatopsis as a subgenus of Curimata in his description of C. macrolepis, a species that has scale poring developed only on the anterior portion of the laterosensory system of the body. That character was, in turn, used by Eigenmann and Eigenmann (1889b) as part of their definition of Curimatopsis as a genus and in their description of Curimatopsis microlepis, by Ahl (1931) when proposing Curimatopsis macrocephalus, and by Géry (1964a) for his Curimatopsis evelynae. Other authors who have also used Curimatopsis for species with incompletely pored lateral lines are Meinken (1933) in his description of Curimatopsis saladensis and Ahl (1934) when he described Curimatopsis maculatus. Vari (1982a) redefined Curimatopsis on the basis of a number of derived innovative characters and described C. crypticus, a species with an incompletely pored lateral line. That attribute also characterized C. myersi, subsequently described by Vari (1982b). Both Curimata vanderi Britski (1980) and C. punctata Vari and Nijssen (1986) have lateral line scale poring limited to the anterior portion of the body, but were not placed by their authors in Curimatopsis.

The nominal species with incomplete poring of the laterosensory canal system of the body fall into two distinct groups, those assignable to Curimatopsis as defined by Vari (1982a) and in this study (C. macrolepis, C. microlepis, C. microcephalus ( = C. macrolepis), C. evelynae, C. crypticus, and C. myersi), and those assigned herein to Cyphocharax (C. saladensis, C. maculatus, C. vanderi, and C. punctata). The Curimatopsis species are definable by a number of unique innovative synapomorphies (see “Synapomorphy List and Phylogenetic Reconstruction”). Cyphocharax, although not itself delimited by any unique characters, does share numerous synapomorphies at different levels of universality with Potamorhina, Curimata, Psectrogaster, Steindachnerina, Curimatella, and Pseudocurimata; characters not found in Curimatopsis species. Thus the data overwhelmingly indicate that the clade recognized as Curimatopsis and the assemblage of species of Cyphocharax with incomplete poring of the lateral line are not closely related to each other (Curimatopsis maculatus Ahl, which has an incomplete lateral line, is based on a juvenile of a Cyphocharax species that has a fully pored lateral line as an adult). The reduced development of portions of the laterosensory canal system of the body in the two assemblages is considered homoplasious, although constituting a synapomorphy for each of the assemblages at lower levels of universality. A similar situation involves the absence of the laterosensory canal segment in the first infraorbital; a reduction that characterizes the species having the reduced poring of the lateral line and in addition Steindachnerina binotata. Again the absence of that canal segment is judged to be homoplasious within the family given the overall most parsimonious hypothesis of relationships within the Curimatidae. That character is nonetheless an evident synapomorphy for Curimatopsis on the one hand, and the assemblage formed by Cyphocharax saladensis, C. vanderi, and C. punctata on the other, and is an autapomorphy for Steindachnerina binotata.

Reductive characters present problems relative to their utility in the generation of phylogenetic hypotheses. Some authors (e.g., Hecht and Edwards, 1977) have noted the potential difficulties in determining homologies when losses or reductions are being studied since it is not possible to critically compare a character that is absent. Similarly Weitzman and Vari (1988) discussed the difficulties in discriminating paedomorphic features from primitive characters in the absence of a phylogenetic framework. Those problems are well exemplified by the reductions in the laterosensory canal segments noted above, and the need for phylogenetic studies to evaluate such patterns emphasized by Weitzman and Vari is well demonstrated. By focusing on a single reductive body system, the reduced lateral line poring, Meinken (1933) and Ahl (1934) aligned their nominal species (C. saladensis and C. maculata respectively) with Curimatopsis (sensu stricto). The phylogenetic hypothesis based on a more extensive set of characters, internal and external, indicates in contradistinction that those reductions were independently achieved in those two species and Curimatopsis.

Weitzman and Vari (1988) also discussed the correlation between paedomorphic features and reductions in relative body sizes. Although none of the curimatid species with reductive characters fits the size limit for miniatures proposed in that study, those authors noted that miniaturization must be dealt with as a relative concept. Miniatures must be judged relative to the body sizes of their immediate outgroups. Within that definition, some of the curimatids with reductive features could perhaps be considered miniatures. Four of the Curimatopsis species (macrolepis, evelynae, myersi, and crypticus) are all among the smallest species of curimatids, being much smaller than any species of the Prochilodontidae, which is the sister group to the Curimatidae. Species of Curimatopsis are also of smaller maximum body size than the species of their sequential proximate sister groups within the Curimatidae: Potamorhina, whose species achieve 205–265 mm SL; Curimata, whose members reach 112–235 mm SL; and Psectrogaster, the species of which grow to 130–210 mm SL.

Curimatopsis is definable on the basis of sixteen synapomorphies. Five of these (SYNAPOMORPHIES 40, 41, 42, 46, and 50) are reductive, two involving losses of autogenous ossifications (the second set of uroneurals, SYNAPOMORPHY 40, and the antorbital, SYNAPOMORPHY 41). The other three reductive synapomorphies for the genus involve reductions in the degree of development of the laterosensory canal systems of the head and body, along with a reduction or loss of some of the dermal ossifications associated with that sensory system. Although Curimatopsis species do not as adults approach the standard lengths of members of the Prochilodontidae or proximate clades to that genus within the Curimatidae, there is nonetheless more than a two-fold range between the standard lengths of the largest examined individuals of C. evelynae (40.1 mm SL) and C. microlepis (99.4 mm SL). Across the range of lengths within the genus there is a correlation between body size and the degree of expression of various reductive, apparently paedomorphic features. Curimatopsis microlepis and C. macrolepis which achieve standard lengths of 99.4 mm and 60.6 mm respectively do not demonstrate any reductive features beyond those general for the genus. The species of the sister group to the clade formed by those genera, the lineage consisting of C. evelynae, C. crypticus, and C. myersi, range in size from 40.1 mm to 48.7 mm SL. That clade is characterized in part by an additional reductive feature, the absence of an ossified sixth infraorbital (Curimatopis SYNAPOMORPHY G). The trend to smaller adult body sizes is most pronounced in Curimatopsis evelynae, which also autapomorphously possesses a further series of reductive characters involving the laterosensory canal system (Curimatopsis SYNAPOMORPHIES I, J, H). These losses are among those “typical” for miniatures according to Weitzman and Vari (1988), and the progressive increase in the number of paedomorphic features would be expected if there is a correlation between a reduction in body size and a truncation of developmental sequences. Further studies are necessary to determine whether the evident correlation between reduced size and an increase in apparently paedomorphic features that is found in Curimatopsis is a general pattern across the Characiformes.

The concept of miniatures might also be applied to at least some of the Cyphocharax species with reductive features. Again these are species smaller than the other members of the genus and proximate outgroups, although one species, Cyphocharax saladensis, does achieve relatively large body sizes (58.3 mm SL). A more definitive statement on possible paedomorphosis in Cyphocharax must await the proposal of a phylogenetic hypothesis for those members of the genus of reduced body size.

Comparisons with Previous Classifications

A variety of alternative classificatory schemes have been proposed for, and applied to, the species of the Curimatidae. One extreme in this century was advanced by Eigenmann (1910:420–422) who recognized only seven genera for the known species of Curimatidae, exclusive of Anodus and Eigenmannina. At the opposite extreme, less than four decades later Fernández-Yépez (1948), describing 17 new genera, recognized 29 genera. Fowler (1906, 1913b, 1940, 1941) independently advanced a number of genera that have been inconsistently recognized since their proposal.

The complexity of the alternative previous classifications of the Curimatidae makes it inefficient to discuss comparative merits and problems of each of those systems. Rather I will only discuss those two arrangements that have been most widely utilized: Eigenmann (1910), and Fernández-Yépez (1948). Independently and in common, these demonstrate problems typical of the diverse classificatory schemes proposed for the Curimatidae.

Eigenmann's (1910) classification consisted of the following: one large genus, Curimatus, containing about 71% of the 66 species then recognized in the family; four genera (Psectrogaster, Curimatella, Curimatopsis, and Semitapicis) with two to eight nominal species; and two monotypic genera (Potamorhina and Gasterotomus). Among the genera recognized by Eigenmann (1910) with two or more species, only one, Curimatopsis, reflected a monophyletic unit in the phylogeny proposed in the present study. Psectrogaster as defined herein was divided by Eigenmann (1910) between that genus (sensu stricto) and Curimatus (C. isognathus and C. rutiloides). Similarly Curimatella of Eigenmann (1910) agrees relatively well although not completely with the concept of that genus proposed in this study, but Curimatus dorsalis Eigenmann and Eigenmann was retained in Curimatus by Eigenmann (1910), whereas currently available data indicate that its closest relatives are the Curimatella species of Eigenmann's (1910) classification.

Eigenmann's (1910) Curimatus, his most inclusive genus, has components that are now assignable to nearly all the curimatid lineages described herein, including the following genera (with Eigenmann's, 1910, species): Cyphocharax (Curimatus spilurus, C. gillii); Curimatella (Curimatus dorsalis, C. leucostictus); Steindachnerina (Curimatus nasus, C. conspersa); Pseudocurimata (Curimatus troschelii, C. brevipes); Curimata (Curimatus aspera, C. mivartii); and Psectrogaster (Curimatus rutiloides, C. isognathus). Reference to Figure 44 shows that Curimatus in the sense of Eigenmann (1910) is thus scattered across the phylogeny proposed here, and so does not form a monophyletic assemblage. Also, components placed by Eigenmann (1910) in other nominal genera (e.g., Curimatella (sensu stricto), Psectrogaster (sensu stricto), Semitapicis (in part)) would have to be returned to Curimatus as defined by Eigenmann in order for that genus to be monophyletic.

This situation exemplifies one of the most common consequence of classifications predicated primarily on concepts of external differences. The taxa with some externally obvious, often derived, characters were separated in their own genera. As a result the remaining species were left in an assemblage definable only by the absence of the distinctive features of the excluded taxa. Such taxa consisting of residual species were in most instances non-monophyletic, or if monophyletic, could not be recognized as such from data then available.

Fernández-Yépez (1948) drastically subdivided the Curimatidae into 27 genera (not including Anodus and Eigenmannina) of which ten were monotypic. That high percentage of monotypy and the large number of genera with small numbers of species would make generic level comparisons between that system and the results of this study tedious and confusing. As a consequence the best framework to evaluate Fernández-Yépez's (1948) classification is to compare the distribution of species within his classification with the groupings arrived at in the present study.

No lineages were found to be common to the two schemes of relationship, with drastic differences between them occurring in most instances. A case by case comparison would again be tedious but several examples will be given to provide a sense of the differences. The genus Potamorhina of the present study, a lineage well corroborated by multiple synapomorphies, is subdivided between the tribes Potamorhini and Curimatini under Fernández-Yépez's (1948) system. Both of those taxa, in turn, contained species assigned to all of the other lineages recognized herein, with the exception of Curimatopsis. Curimata, as defined herein, was scattered across eight genera in Fernández-Yépez's scheme, with individual Curimata species aligned by that author with species considered to belong to Cyphocharax, Steindachnerina, Psectrogaster, and Curimatella in this paper. Furthermore the individual lineages containing species of Curimata did not form a discrete subunit in Fernández-Yépez's (1948) phylogenetic scheme. Comparable problems with Fernández-Yépez's (1948) “phylogenetic tree” exist relative to each of the other lineages recognized in this study. Thus the congruence of Fernández-Yépez's (1948) classification with the phylogeny proposed herein is judged to be minimal.

To a large extent the cited problems appear to be the result of Fernández-Yépez's (1948) dependence on a few characters as the basis for his classification. One of the most significant of those features was the degree of development of various prepelvic, postpelvic, and predorsal angles in the body walls, with that being supplemented by characters involving scalation on the caudal fin rays, relative fin position, mouth form and position, and degree of development of the laterosensory canal system on the body. Many of those noted characters do constitute synapomorphies at some levels of universality and thus are potentially useful in generating phylogenetic hypotheses. Nonetheless they also demonstrate a notable degree of convergence within the Curimatidae in the context of the phylogeny proposed herein. Such convergence can only be detected by the examination of a broader spectrum of internal and external characters than those utilized by Fernández-Yépez (1948) and other authors. This problem is best exemplified by the convergencies in the laterosensory canal system reductions that have been discussed in the previous sections. Above and beyond questions of character homology and homoplasy, Fern´ndez-Yépez's (1948) classification also demonstrates the weaknesses already commented on relative to the Eigenmann (1910) scheme—the separation of phenetically externally distinctive taxa into their own monotypic genera, leaving non-monophyletic residual amalgams of externally generalized species typically recognized as genera.

Although both authors used primarily external features as the basis for their classifications, the noted problems in their taxonomic schemes are not a consequence of the reduced utility of external characters in phylogenetic reconstructions, but rather an outgrowth of the methodologies utilized. The problems noted above for the classifications of Eigenmann (1910) and Fernández-Yépez (1948) are, in turn, typical of the classifications proposed by other authors who have also dealt with the family (e.g., Fowler, 1975).

Resumo

A família Curimatidae consiste de mais de 120 espécies nominais que habitam uma ampla série de ecossistemas de âgua doce neotropicais, variando desde os lagos e rios de curso lento das terras baixas até os riachos de curso mais r´pido das elevações médias ao longo do sopé dos Andes e das terras altas do escudo das Guianas e do escudo do Brasil. Curimatídeos ocorrem a oeste e ao norte dos Andes nos rios das vertentes do Pacífico, desde o sul da Costa Rica até a norte do Peru, e nas drenagens do Caribe no noroeste da América do Sul, incluindo os sistemas do rio Atrato, rio Magdalena e lago Maracaibo. Os maiores números de espécies de curimatídeos ocorrem nas vertentes atlânticas da América do Sul, desde o rio Orinoco, passando pela bacia Amazônica e os rios costeiros das Guianas, Brasil, Uruguai e Argentina, até ao sul de Buenos Aires.

Classificacões prévias da família nào foram baseadas em hipóteses de relações evolutivas dentro da família. Em lugar disso estas propuseram novos gêneras e subgêneros com base em graus de similaridade ou diferença e, assim mesmo, usando somente caracteres externos. A “ârvore filogenètica” formulada por Fernândez-Yépez (1948) é uma representaçâo direta de sua chave dicotòmica para os gêneros da famíilia e nào de um verdadeiro esquema filogenètico. Como consequência desses e outros problemas, muitas das unidades taxonõmicas situadas acima do nível de espécie reconhecidas em classificòes prévias nào representam agrupamentos naturais. Os estudos relatados neste trabalho foram realizados tendo em vista a formulaçâo de uma hipótese, baseada em caractères derivados distintos, quanto às relações filogenéticas a nivel supra-específico dentro da família Curimatidae.

O esqueleto e outros sistemas anatõmicos das espécies da famflia Curimatidae foram estudados com o fam de se investigar a hipótese de que esta é uma subunidade da ordem Characiformes, e também de se propor uma hipótese quanto às relações filogenéticas dentro da família. Sinapomorfias associadas com o aparelho branquial, complexo buco-faringeano, arco hióide, antorbital, infra-orbitais, aparelho opercular, “ligamentum primordiale,” maxilas, arco palatino e neurocrànio sào congruentes com a hipótese de que a família é uma linhagem monofìlética. Caracteres adicionais num subgrupo desses sistemas sào congruentes com a hipótese proposta por Vari (1983) quanto a Curimatidae e Prochilodontidae serem grupos-irmâos. A posse em comun de caracteres derivados nos sistemas corporais citados anteriormente, assim como no complexo hipural, nos raios da nadadeira caudal e na coluna vertebral definem subunidades naturais dos Curimatidae. Esses caracteres apoiam uma hipótese filogenètica com quatro dicotomias sequenciais e uma politomia terminal. Sete linhagens, reconhecidas como gêneras (Curimatopsis, Potamorhina, Curimata, Psectrogaster, Steindachnerina, Pseudocurimata, e Curimatella), sào consideradas monofiléticas com base na posse em comum de caractères derivados. Nào foram encontrados caractères derivados únicos que definam Cyphocharax, o oitavo gènero reconhecido.

A hipótese para relaçôes filogenéticas intra-familiares obtida neste estudo é incongruente, em diferentes graus, com os esquemas de classificaçâo propostos por Eigenmann & Eigenmann (1889b), Eigenmann (1910), Fowler (1975), e Géry (1977b). Existem numerosas diferenças, em todos os níveis taxonõmicos, entre o esquema de interrelações proposto neste estudo e a “ârvore filogenètica” apresentada por Fernândez-Yépez (1948). A transferência, proposta pela primeira vez por Roberts (1974), dos gêneras Anodus Spix e Eigenmannina Fowler, tradicionalmente incluídos nos Curimatidae, para os Hemiodontidae, è uma mudança congruente com os resultados obtidos por Vari (1983), estando de acordo com a distribuiçào de vârios caracteres adicionais considerados como derivados descobertos durante o presente estudo.

Oito gêneras: Curimatopsis Steindachner (1876), Potamorhina Cope (1878), Curimata Bosc (1817), Psectrogaster Eigenmann & Eigenmann (1889a), Steindachnerina Fowler (1906), Pseudocurimata Fernândez-Yépez (1948), Curimatella Eigenmann & Eigenmann (1889b) e Cyphocharax Fowler (1906) sào reconhecidos na família. Curimatichthys Fernândez-Yépez (1948) é considerado um sinònimo de Curimatopsis. Potamorhina è redefinida de maneira a incluir Gasterotomus Eigenmann (1910), Gasterostomus Fernández-Yépez (1948), Suprasinelepichthys Fernândez-Yépez (1948), e Potamorrhina Braga & Azpelicueta (1983). Curimata Bosc (1817) tem nove sinõnimos juniores: Semitapicis Eigenmann & Eigenmann (1889b), Peltapleura Fowler (1906), Acuticurimata Fowler (1941), Allenina Fernândez-Yépez (1948), Lambepiedra Fernândez-Yépez (1948), Bitricarinatra Fernândez-Yépez (1948), Bondichthys Whitley (1953), Stupens Whitley (1954), e Semitapiscis Braga and Azpelicueta (1983). Très gêneras sào inclui’dos em Psectrogaster. Estes sào: Pseudopsectrogaster Fernândez-Yépez (1948), Hamatichthys Fernândez-Yépez (1948) e Semelcarinata Fernândez-Yépez (1948). Rivasella e Curimatorbis, ambos propostos por Fernândez-Yépez (1948), sâo colocados como sinõnimos de Steindachnerina Fowler (1906). Curimatella tem très sinõnimos juniores: Apolinarella, Walbaunina e Lepipinna, todos de autoria de Fernândez-Yépez (1948). Cyphocharax tem quatre sinõnimos: Xyrocharax Fowler (1913b), Hemicurimata Myers (1929), Curimatoides Fowler (1940) e Cruxentina Fernândez-Yépez (1948).

Caracteres homoplâsicos em relaçâo à filogenia proposta sâo discutidos em termos da sua distribuiçao dentro e fora da família Curimatidae e também quanto a serem caracteres inovadores ou redutivos.

Caracteres redutivos, envolvendo o grau de desenvolvimento do sistema de canais lâtero-sensoriais cefâlicos e corporais presentes nas espécies de Curimatopsis e num grupo de espécies de Cyphocharax, revelaran-se convergentes. Estes caracteres pedomórficos sâo evidentemente uma consequência da miniaturizaçâo relativa dessas espécies em comparaçâo com seus extra-grupos mais próximos.

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Tabulations within text (lists of data, often in parallel columns) can be typed on the text page where they occur, but they should not contain rules or numbered table captions.

Formal tables (numbered, with captions, boxheads, stubs, rules) should be submitted as carefully typed, double-spaced copy separate from the text; they will be typeset unless otherwise requested. If camera-copy use is anticipated, do not draw rules on manuscript copy.

Taxonomic keys in natural history papers should use the aligned-couplet form for zoology and may use the multi-level indent form for botany. If cross referencing is required between key and text, do not include page references within the key, but number the keyed-out taxa, using the same numbers with their corresponding heads in the text.

Synonymy in zoology must use the short form (taxon, author, year:page), with full reference at the end of the paper under “Literature Cited.” For botany, the long form (taxon, author, abbreviated journal or book title, volume, page, year, with no reference in “Literature Cited”) is optional.

Text-reference system (author, year: page used within the text, with full citation in “Literature Cited” at the end of the text) must be used in place of bibliographic footnotes in all Contributions Series and is strongly recommended in the Studies Series: “(Jones, 1910:122)” or “…Jones (1910:122).” If bibliographic footnotes are required, use the short form (author, brief title, page) with the full citation in the bibliography.

Footnotes, when few in number, whether annotative or bibliographic, should be typed on separate sheets and inserted immediately after the text pages on which the references occur. Extensive notes must be gathered together and placed at the end of the text in a notes section.

Bibliography, depending upon use, is termed “Literature Cited,” “References,” or “Bibliography.” Spell out titles of books, articles, journals, and monographic series. For book and article titles use sentence-style capitalization according to the rules of the language employed (exception: capitalize all major words in English). For journal and series titles, capitalize the initial word and all subsequent words except articles, conjunctions, and prepositions. Transliterate languages that use a non-Roman alphabet according to the Library of Congress system. Underline (for italics) titles of journals and series and titles of books that are not part of a series. Use the parentheses/colon system for volume (number): pagination: “10(2):5–9.” For alignment and arrangement of elements, follow the format of recent publications in the series for which the manuscript is intended. Guidelines for preparing bibliography may be secured from Series Section, SI Press.

Legends for illustrations must be submitted at the end of the manuscript, with as many legends typed, double-spaced, to a page as convenient.

Illustrations must be submitted as original art (not copies) accompanying, but separate from, the manuscript. Guidelines for preparing art may be secured from Series Section, SI Press. All types of illustrations (photographs, line drawings, maps, etc.) may be intermixed throughout the printed text. They should be termed Figures and should be numbered consecutively as they will appear in the monograph. If several illustrations are treated as components of a single composite figure, they should be designated by lowercase italic letters on the illustration; also, in the legend and in text references the italic letters (underlined in copy) should be used: “Figure 9b.” Illustrations that are intended to follow the printed text may be termed Plates, and any components should be similarly lettered and referenced: “Plate 9b.” Keys to any symbols within an illustration should appear on the art rather than in the legend.

Some points of style: Do not use periods after such abbreviations as “mm, ft, USNM, NNE.” Spell out numbers “one” through “nine” in expository text, but use digits in all other cases if possible. Use of the metric system of measurement is preferable; where use of the English system is unavoidable, supply metric equivalents in parentheses. Use the decimal system for precise measurements and relationships, common fractions for approximations. Use day/month/year sequence for dates: “9 April 1976.” For months in tabular listings or data sections, use three-letter abbreviations with no periods: “Jan, Mar, Jun,” etc. Omit space between initials of a personal name: “J.B. Jones.”

Arrange and paginate sequentially every sheet of manuscript in the following order: (1) title page, (2) abstract, (3) contents, (4) foreword and/or preface, (5) text, (6) appendixes, (7) notes section, (8) glossary, (9) bibliography, (10) legends, (11) tables. Index copy may be submitted at page proof stage, but plans for an index should be indicated when manuscript is submitted.