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Smithsonian Contributions to Paleobiology, number 57, 29 pages, 17 figures, 1985.?Seven genera of giant camels occurred in North America during the interval from the late Clarendonian to the early Holocene. Aepycamelus was the first camel to achieve giant size and is the only one not in the subfamily Camelinae. Blancocamelus and Camelops are in the tribe Lamini, and the remaining giant camels Megatylopus, Titanotylopus, Megacamelus, Gigantoca- melus, and Camelus are in the tribe Camelini. Megacamelus is a late Hemphil? lian giant camel most closely related to Gigantocamelus. Titanotylopus is reserved for the brachyodont form from the Irvingtonian of Nebraska, and Gigantocamelus is reinstated for the broad-chinned, Blancan form. 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 trilobite Phacops rana Green. Library of Congress Cataloging in Publication Data Harrison, Jessica A. Giant camels from the Cenozoic of North America. (Smithsonian contributions to paleobiology ; no. 57) Bibliography: p. Supt. of Docs, no.: SI I.30:.57 \. Camels, Fossil. 2. Paleontology?Cenozoic. 3. Paleontology?North Amer? ica. I. Title. II. Series. QE701.S56 no. 57 [QE882.U3] 560s [599.73'6] 84-600303 Contents Page Introduction I Acknowledgments I Phylogenetic Relationships 1 Aepycamelus 4 Megatylopus 5 Titanotylopus 7 Gigantocamelus 8 Megacamelus 10 Megacamelus merriami, new combination I I Camelus 21 Blancocamelus 23 Camelops 24 Summary 24 Literature Cited 26 111 FRONTISPIECE.?Reconstruction of the head of Megacamelus merriami. Giant Camels from the Cenozoic of North America Jessica A, Harrison Introduction Throughout the later Cenozoic, camels often figure as an abundant and diverse element of any fauna in which they occur. Until the late Pleis? tocene, when the group fell on hard times, the Camelidae must be accounted one of the more successful ungulate families. As in many other herbivore families, the earliest members of the Camelidae were of small body size. However, a trend toward gigantism can be observed throughout the later Cenozoic, from the Clar? endonian into the Holocene. Descriptions of very large camels are almost as abundant in the literature as their remains in late Cenozoic faunas. T h e confusing taxonomic his? tory of the giant camels is such that, for every specific identification, there are many more re? ferrals to "camelid, large, gen. et sp. indet." The purpose of this paper is to provide a temporal, geographic, and systematic framework for the large, late Cenozoic camels. ACKNOWLEDGMENTS.?I am grateful for the use of specimens from the Frick Collection, De? partment of Vertebrate Paleontology, American Museum of Natural History (F:AM), the Univer? sity of California Museum of Paleontology Jessica A. Harrison, formerly Department of Paleobiology, Na? tional Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, now Research Associate, Department of Geosciences, University of Arizona, Tucson, Arizona 85721. (UCMP), the University of Nebraska State Mu? seum (UNSM), and the University of Kansas Museum of Natural History (KUVP). I very much appreciate careful and constructive reviews by George Corner, Michael Voorhies, John Breyer, and Robert Emry. Drs. Corner and Voorhies were particularly generous in sharing with me their new information on Titanotylopus. The frontispiece was done by Robert Hynes. Phylogenetic Relationships The cladogram in Figure 1 summarizes rela? tionships within the Camelinae. It is interesting to note that the trend toward gigantism is far more apparent in the Camelini than in the Lam? ini. All of the genera comprising the Camelini can be called giants, but only two of the Lamini, Camelops and Blancocamelus, achieve a formida? ble body size. Aepycamelus, the only noncameline genus, represents the camels' earliest experimen? tation with gigantism. The characters appearing at nodes 1 through 35 in the cladogram are listed below. The com? position and apomorphies of the Protolabidini are from Honey and Taylor (1978:419-420), whereas those of the Lamini and Camelini ap? peared in part in Harrison (1979:3-8). More detailed discussion of the characters may also be found in those papers. SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Camelinae 1 Protolabidini Tr Lamini .^ 1 r Camelini T <# 9 J> x'^ ..^ ^^ V y yX/M / / / / / / / / ^ / -. c cfl o to E n 4 CO CM CO CM S < l i ?"K" (N S t 00 _ a CM 3 CO o 1^ NUMBER 57 15 FIGURE 9.?Megacamelus merriami, new combination, from Keams Canyon, Arizona, F:AM 23202, skull: 1, dorsal view; 2, occlusal view. (X VA.) well posterior to the occipital condyles. The sag? ittal crest is likewise well developed. The orbit is circular in outline followed by a strong postor- bital bar. A triangular lacrimal vacuity is present in most of the Keams Canyon M. merriami, but it is a highly variable feature. In one specimen. F:AM 23202, it is present on the left side of the skull, but reduced to a slit on the right side (Figure 9). Another skull, F:AM 23202A, bears well-developed lacrimal vacuities on both sides (Figure 10). Although Meade (1945:531) re? ported the presence of a lacrimal vacuity in M. spatulus from Mt. Blanco, Hibbard and Riggs (1949:846) reported its absence and, moreover, suggested that the opening in the Mt. Blanco skulls could represent an artifact of preservation. The upper dentition consists of V, C\ p'-^^, M^"^. F is always present and, as mentioned above, is large and caniniform. C' is large and deviates slightly from a vertical orientation. Pre? sumably, when Barbour and Schultz (1939:24) stated that the canines of the Keams Canyon 16 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 10.?Megacamelus merriami, new combination, from Keams Canyon, Arizona, F:AM 23202A, skull: 7, dorsal view; 2, occlusal view. (X '/4.) Note the large lacrimal vacuities. camel were not enlarged, it was in comparison to the extreme development observed in Giganto? camelus spatulus and Titanotylopus nebraskensis. P' is caniniform and only slightly smaller than F . P^ is large with an incomplete internal crescent. P'' is not much longer than P'^ but much wider due to its complete internal crescent. Only the parastyle shows much development on P"*, but a strong parastyle and mesostyle are present on each molar. The teeth are higher crowned than those of Megatylopus gigas or Titanotylopus ne? braskensis. The mandible is long and massive but still smallei" than that of Gigantocamelus spatulus or Titanotylopus nebraskensis. The mandibular pro? portions of M. merriami agree well with those of G. spatulus; however, M. merriami does not dis? play the degree of variation in the symphyseal NUMBER 57 17 T A B L E 4.?Measurements (cm) o f the postcrania of Megacamelus merriami, new combination, from Keams Canyon (O.R.= observed range, X = sample mean, s.d. = standard deviation). Element Atlas length of centrum posterior height Scapula maximum length maximum width glenoid fossa antero? posterior transverse Humerus length distal width across trochlea Radius-ulna maximum length articular length proximal width distal width Metacarpus length proximal width distal width Femur length proximal width distal width width of patellar surface No. 2 1 2 1 3 3 1 5 4 4 6 5 7 8 7 1 1 2 3 O R . 6.75-6.80 9.36 61.53-64.06 38.35 9.37-10.56 9.17-10.61 53.27 10.60-11.70 72.65-85.70 66.03-75.50 10.19-11.52 10.40-12.62 48.39-54.29 8.11-11.64 11.38-12.30 60.89 16.07 13.98-15.34 5.07-5.79 X s.d. 6.77 62.79 9.87 9.66 11.14 80.33 71.22 10.87 0.43 11.39 51.08 2.07 9.12 1.10 11.88 0.33 14.66 5.46 Element Tibia length distal width Astragalus length (tibial to tarsal surface) medial lateral distal width Calcaneum length maximum antero? posterior Metatarsus length proximal width distal width Proximal phalanx length proximal width distal width Medial phalanx length proximal width distal width Distal phalanx length width of articular surface No. 1 2 7 7 7 4 4 5 2 4 21 21 22 18 18 17 6 6 O.R. 67.00 10.95-11.45 8.19-8.98 8.85-9.80 6.03-6.65 17.68-19.56 7.21-8.30 48.37-50.58 8.06-9.37 10.01-10.75 11.05-13.80 4.55-5.73 3.82-5.14 7.22-8.47 3.74-4.99 3.26-4.21 3.16-4.16 2.45-2.80 X s.d. 11.20 8.57 0.34 9.47 0.30 6.39 0.21 18.64 7.90 49.44 8.71 10.35 12.41 0.84 5.08 0.35 4.42 0.41 7.76 0.34 4.19 0.27 3.79 0.25 3.71 0.34 2.60 0.13 region observed in G. spatulus by Meade (1945:532) or Hibbard and Riggs (1949:847). Meade, in the Mt. Blanco sample, and Hibbard and Riggs, in the Keefe Canyon sample, found jaws with widely splayed and canines and trans? versely arrayed incisors as well as jaws with more vertically oriented canines and more convention? ally arrayed incisors. Hibbard and Riggs (1949), Webb (1965), and Breyer (1976) have attributed such variation to sexual dimorphism. In the Keams Canyon sample the incisors are procum? bent and arrayed in a more shallow arc than in Titanotylopus. The canines are very large, but only slightly splayed. No specimen displays the degree of canine flare and incisor-row bluntness characteristic of G. spatulus (Cope, 1893, pi. 21; Barbour and Schultz, 1939, fig. 9; Meade, 1945, pi. 54; Hibbard and Riggs, 1949, fig. 8). A groove is present between the median incisors on the ventral symphyseal surface, as noted by Cope (1893:71) and Meade (1945:532). The lower dentition consists of Ii_3, Ci, Pi,3,4, Mi_3. The incisors have spatulate crowns that with much wear assume a more rounded, peg- 18 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 11.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 1, 4, F:AM 23216, mandible, occlusal and lateral views; 2, 3, F:AM 23239A, partial ramus bearing deciduous Pa-4 and M| emerging, occlusal and lateral views. (X '/4.) like appearance. The canines bear the strong anterointernal and posterior enamel ridges typi? cal of G. spatulus. Pi is present in all specimens and usually well developed. An exception is F:AM 23218, one of the smallest individuals, in which Pi is correspondingly small. The cheek tooth series is quite similar to that of Af. spatulus. Meade (1945:533) reports an anteroexternal style or "llama buttress" on Ms.3 of one specimen and notes the presence of this feature in figures of M. spatulus from Lisco. No indication of a "llama buttress" is present in M. merriami. The limbs and feet of M. merriami, especially the metapodials and phalanges, do not exhibit the shortening in relation to the basal length of the skull seen in G. spatulus. Hence, Barbour and NUMBER 57 19 FIGURE 12.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 1, 2, F:AM 104293, atlas, dorsal and ventral views; 3, F:AM 104281, sixth cervical vertebra, lateral view; 4, 5, F:AM 104284, axis, dorsal and ventral views; 6, F:AM 23245, left scapula, lateral view. (X '/4.) Schultz (1939:24) remarked that "the skeletal elements appear to be more massive in the Ne? braska form" (= G. spatulus). The limbs of M. merriami are, however, shorter and stockier than those of Megatylopus. DISCUSSION.?Megacamelus merriami is most closely related to Gigantocamelus spatulus but dif? fers from it in the presence of the large, canini? form F , smaller size, less shortened limbs, and lower-crowned teeth. Breyer (1983:305) re- 20 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY W' -*r U^-f :T*" . - } - . ?3-f- *^ r FIGURE 13.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 7, 2, F:AM 23256, humerus, anterior and posterior views; 3, 4, F:AM 23262, radius-ulna, anterior and posterior views. (X %.) NUMBER 57 21 ferred the Keams Canyon material to Titanotylo? pus nebraskensis on the basis of the projection of the mandibular symphysis beyond the canines. This condition is primitive for camelines and hence not a valid criterion. Moreover, several characters such as the presence of Pi in all spec? imens, greater degree of hypsodonty, and the greater distance between Ci and P3 preclude the referral of the Keams Canyon camel to Titanoty? lopus. Camelus Linnaeus, 1758 TYPE-SPECIES.?Camelus dromedarius Lin? naeus, 1758:65. Camelus is the smallest of the giant camels. The two extant species, G. dromedarius (mono- gibbose) and C. bactrianus (digibbose), range throughout most of the arid and semi-arid re? gions of the Old World. Camelus bactrianus is native to Chinese Turkestan and Mongolia, where small wild populations still exist (Walker, 1964:1374). Both C. bactrianus and C. dromedar? ius have been domesticated for several thousand years, and the original native range of the latter species can no longer be determined. Camelus has an extensive fossil record in the Pleistocene ofthe Old World and has been found in association with human artifacts and remains (Gauthier-Pilters and Dagg, 1981:5). Camels mi? grated from North America via Beringea near the end of the Tertiary, probably during the late Ruscinian. Camelus (Paracamelus) Schlosser (1903) occurs in several late Pliocene localities in the People's Republic of China. As yet no fossil material of Camelus or Paracamelus has been recovered from North America. FIGURE 14.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 7, 2, F:AM 104311, scaphoid, medial and lateral views; 3, 4, F:AM 104323, lunar, medial and lateral views; 5, 6, F:AM 104325, cuneiform, medial and lateral views; 7, 8, F:AM 104312, pisiform, medial and lateral views; 9, 10, F:AM 104359, trapezoid, posteromedial and anterolateral views; 7 7, 72, F:AM 104360, magnum, proximal and distal views; 13, 14, F:AM 104343, unciform, proximal and distal views; 15, 16, F:AM 23279, metacarpus, anterior and posterior views. (X '/4.) 22 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY FIGURE 15.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 7, 2, F:AM 23293, femur, anterior and posterior views; 3, 4, F:AM 23296, tibia, anterior and p<>slfii(jr views. (X '/i.) NUMBER 57 23 Fii wi ^ ^ 1 3 ^ ^ 1 4 t.? 1 6 ^.ik 22 FIGURE 16.?Megacamelus merriami, new combination, from Keams Canyon, Arizona: 1-3, F:AM 104239, calcaneum, lateral, medial, and anterior views; 4, 5, F:AM 104255, proximal phalanx, anterior and posterior views; 6, 7, F:AM 104222, medial phalanx, anterior and posterior views; 8-10, F:AM 104231, astragalus, anterior, posterior and lateral views; 77, 72, F:AM 104226, distal phalanx, anterior and posterior views; 13, 14, F:AM 104379, ectocunei? form, proximal and distal views; 15, 16, F:AM 104366, cuboid, proximal and distal views; 77, 18, F:AM 23307, metatarsus, anterior and posterior views; 19, 20, F:AM 104310, navicular, proximal and distal views; 27, 22, F:AM 104375, distal fibula, medial and lateral views. (X '/4.) Blancocamelus Dalquest, 1975 TYPE-SPECIES.?Blancocamelus meadei Dal? quest, 1975:37. This genus is represented solely by B. meadei, described by Dalquest (1975:37) from Mt. Blanco, Texas. Dalquest noted that although Meade (1945:538) was aware of the uniqueness of this camel, he mistakenly applied to it an unpublished name, Leptotylopus percelsus, from a 1924 manuscript of W.D. Matthew. As used by Meade, the name was a nomen nudum. T h e taxon to which Matthew had applied the name in manuscript was subsequently identified as Ta- nupolama (= Hemiauchenia) blancoensis. Thus, the genus was left without a valid name until Dalquest (1975) proposed Blancocamelus meadei for it. 24 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY Blancocamelus is known only from postcranial elements. Its limbs are exceedingly long, but quite slender, evoking mental images of a giant Hemiauchenia. Indeed, the posterior surface of the proximal phalanx presents an asymmetrical, W-shaped scar for the attachment of the suspen? sory ligament that is quite like that of Hemiauch? enia (Breyer, 1976, fig. 2). Although Meade (1945) and Kurten and Anderson (1980:302) have speculated upon the possible affinities of Blancocamelus and the aepycamelines, I prefer for the present to group it with the lamines. With the exception of a possible occurrence in the Blancan Red Light fauna of Texas (Akersten, 1972:29), Blancocamelus is restricted to the type- locality (Figure 4). Camelops Leidy, 1854 TYPE-SPECIES.?Camelops kansanus Leidy, 1854:172. Camelops is by far the best known of the lam? ines, giant or otherwise. It occurs from the late Blancan into the early Holocene in localities throughout the western United States (Kurten and Anderson, 1980, fig. 15.4). Since its descrip? tion by Leidy (1854:172), the genus Camelops has undergone a bewildering series of synonymies, referrals, and revisions. Much of this morass was clarified by Webb (1965), who followed Savage (1951) in recognizing five species: C. kansanus Leidy (1854:172), C. hesternus (Leidy, 1873:255), C. huerfanensis (Cragin, 1892: 258), C. sulcatus (Cope, 1893:84), and C. minidokae Hay (1927:93). These five species plus C. travis- whitei Mooser and Dalquest (1975:341) were rec? ognized by Kurten and Anderson (1980). Camelops, especially the later species, is very hypsodont with large lacrimal vacuities and marked maxillary fossae. The skull is long and does not display the rostral shortening character? istic of other lamines such as Hemiauchenia, Lama, and Vicugna. The mandible is long with a sharp diastemal crest and uninflected angular proc? esses. The dental formula is I3 C} P? M3. In Ca? melops P and c l are reduced, laterally com? pressed, and recurved rather than enlarged and rounded in cross section as in the giant camelines. Pi.1,3 are lost and P4 are reduced. The molars are relatively narrow with external styles less strongly developed than in the camelines. The limbs of Camelops are sturdy and the metapodials less slender than those of the other lamines. The area of attachment for the suspen? sory ligament on the posterior surface of the proximal phalanx is distinctive (Breyer, 1974, fig. 2B). Camelops hesternus, C. traviswhitei, and C. huerfanensis are the only species considered within the scope of giant camels. More detailed descriptions of Camelops are given in Savage (1951) and Webb (1965). Summary The trend toward gigantism in camelids is first evident in Aepycamelus in the late Clarendonian and continued throughout the rest of the Ceno? zoic (Figure 17). Eight camelid genera are treated as giant camels in this paper. Megacamelus merriami, new combination, is proposed for the large, late Hemphillian camel from Mt. Eden and Keams Canyon. The giant camels from Mt. Blanco, Lisco, and Keefe Can? yon are referred to Gigantocamelus spatulus. Ti? tanotylopus is applied only to T. nebraskensis. Me? gatylopus major is transferred to Aepycamelus. The Camelini were all very large camels, but i^ J- /> y* t^ < / ^ / ? c / Recent Rancholabrean Irvingtonian Blancan Hemphillian Clarendonian Barstovian Hemingfordian [ " [ ^ - ' T ^ FIGURE 17.?Temporal distribution o f the giant camels. NUMBER 57 25 only two giants occur among the Lamini, Came? lops (C. hesternus, C. traviswhitei, and C. huerfa? nensis) and Blancocamelus (if, indeed, this genus belongs in the Lamini and not the Aepycameli- nae). Most camels were considerably smaller. It is intriguing that, in spite of over 40 million years of evolution in North America, and regardless of body size, camels became extinct in their place of origin following successful emigration to South America and Asia. Literature Cited Akersten, W.A. 1972. 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The Saw Rock Canyon Fauna and Its Strati? graphic Significance. Papers ofthe Michigan Acad? emy of Science, Arts, and Letters, 38 :387-411 , fig? ures 1-5. Hibbard, C.W., and W.W. Dalquest 1962. Artiodactyls from the Seymour Formation of Knox County, Texas. Papers ofthe Michigan Acad? emy of Science, Arts, and Letters, 47 :83-99 , figures 1-4. 1966. Fossils from the Seymour Formation of Knox and Baylor Counties, Texas, and Their Bearing on the Late Kansan Climate of That Region. Contribu? tions from the University of Michigan Museum of Paleontology, 21 ( l ) : l - 66 , figures 1-8, plates 1-5. Hibbard, C.W., and E.S. Riggs 1949. Upper Pliocene Vertebrates from Keefe Canyon, Meade County, Kansas. Bulletin of the Geological Society of America, 60 :829-880, figures 1-11, plates 1-5. Honey, J.G., and B.E. Taylor 1978. A Generic Revision of the Protolabidini (Mam? malia, Camelidae), with a description of Two New Protolabidines. 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