3 May 1978 PROC. BIOL. SOC. WASH. 91(1), 1978, pp. 216-221 NEW GENUS AND SPECIES OF AHERMATYPIC CORAL (ANTHOZOA: SCLERACTINIA) FROM THE WESTERN ATLANTIC Stephen D. Cairn.s Abstract.?A new genus and species are described in the subfamily Para.smihinae. Balht/cyathus maculattis Pourtales, 1874 is transferred to the new genus. Both species arc characterized by having paliform lobes before tlie penultimate cycle of septa and an identical method of basal reinforcement. [Scleractinia; Rhizosmilia; Parasmiliinae.l Numerous species have been uncritically placed in the genera Bathy- cyathus and Coenocijulhus. One of these is Balhycyathus maculatus Pourtales, 1874 (= Caryophyllia maculata, Pourtales, 1880; Wells, 1972; Cairns, 1977; Coenocyathus hort.ichi Wells, 1947). A re-examination of B. maculatus indicates that it has endothecal dissepiments (Plate 1, Fig. 8), which would transfer it from the Caryophylliinae to the Parasmiliinae. It is necessary to describe a new parasmilid genus to contain both B. maculatus and another undescribcd .species. Some of the specimens used in this study were collected by the R/V Gerda in the Deep-Sea Biology Program sponsored by the National Geo- grapliic Society. Sliip time was supported by a National Science Foun- dation grant. This is a contribution from the Rosenstiel School of Marine and Atmospheric Science, University of Miami. I would like to thank Dr. Gilbert L. Voss, Rosenstiel School of Marine and Atmospheric Science, for access to the University of Miami collections, and Dr. Frederick M. Bayer, National Museum of Natural History, for the opportiuiity to study the Smithsonian specimens. I am grateful to Dr. John W. Wells, Cornell University, for reviewing the manuscript. All of the specimens listed in this paper are deposited at the National Museum of Natural IIi.story (USNM). Suborder CaryophylHina Vaughan and Wells, 1943 Family Caryophylliidae Gray, 1847 Subfamily Parasmiliinae Vaughan and Wells, 1943 Rhizosmilia, new genus Diagnosis.?Small phaceloid clumped colonies formed by extratentacular budding. Coralhte bases increase in diameter by adding exothecal dissepi- ments over raised costae producing concentric rings of partitioned cham- bers. Paliform lobes present before penultimate cycle. Columella prom- inent, varying from spongy to fascicular (a line of pillars) to lamellar. Endothecal dissepiments present. VOLUME 91, NUMBER 1 217 Type-species.?Rhizosmilia gerdae, n. sp., here designated. Discussion.?Rhizosmilia is easily distinguished from the other genera in the subfamily Parasmiliiuae by a combination of three easily observed characters: it is colonial (clumped phaceloid), has a prominent columella, and has large paliform lobes. The position of the paliform lobes before the penultimate cycle of septa requires explanation. The first paliform lobes to form are the 12 that border the Ss at the 48-septa stage (Fig. la). When a pair of S-, appears within a half-system, one of two things occurs to maintain the paliform lobes before the penultimate cycle: 1) the original P:, may remain stationary before the S-.^ while an independent lobe forms on the accelerated S4 (Fig. lb), or 2) the original ?:) may gradually begin to align with the accelerated S4, maintaining trabecular connections with both S:i and S4 simultaneously (Fig. Ic). With greater development, this transitional paliform lobe be- comes completely aligned and attached to the St (Figs. Id, e). (For ex- ample, every transitional P4 merges with a P3 lower in the fossa.) When the second pair of Sr, occurs in the half-system, if the P3 is still present (case 1), it becomes a transitional lobe and forms the P4. If the P3 has already aligned with the other S4 (case 2), then an independent lobe is formed of equal size on the second S4. In both cases, the final condition is two equal paliform lobes bordering the S4 (penultimate cycle) and no lobe visible before the 83 (Fig. If). Both species in this genus also have a peculiar method of basal rein- forcement. As the corallite increases in size, the edge zone secretes thin costae, up to 2 mm high and 10 mm long, perpendicular to the coralluni wall around the base (Plate 1, Fig. 2). Next, exothecal dissepiments form over the costae, producing a series of chambers around the base. This process may occur several times, producing 4-5 concentric rings of hollow com- partments that substantially increase the basal diameter of the corallite and therefore its stability. If a transverse section is made through the base (Plate 1, Fig. 7), these concentric rings appear identical to Durham's (1949) thecal rings of polycyclic development. The rings described here are, however, structurally and ontogenetically different, since they are formed much later in development by raised costae and exothecal dissepiments, whereas polycyclic thecal rings are an early develoi^mental feature involv- ing overlapping of primitive thecal walls. Furthcnnore, there is no ex- tension of the polyp into the compartments of the costal roots, whereas in polycyclic development, the polyp occupies the area created by the last thecal ring. The identical mode of basal reinforcement also occurs in Phi/llangia and Oxijsmilia. Etymology.?The prefix is derived from the Greek rhiza, meaning root, and pertains to the concentric rings of root-like costal chambers around the base. Gender: feminine. 218 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON VOLUME 91, NUMBER 1 219 4 3 4 I 43 5 45 2 a '5^^535452 f Fig. 1. Diagrams illustrating the maintenance of paliform lobes (p) before penulti- mate cycle of septa (see text). Only one half-system is illustrated; numbers 1?5 correspond to respective septal cycles. Dotted line represents trabecular connection of paliform lobe to adjacent septa. Rhizostnilia gerdae, new species Plate 1, Fig.s. 1-7 Material examined.?Type.s: USNM 46812, holotypic colony (13 coral- lites), USNM 46813, paratypes 36+ corallites), all from Gerda-725, 26?01'N, Plate 1. 1. Rhizosmilia gerdae (holotypic colony): Gerda-lZS, xO.95, USNM 46812; 2. fi. gerdae (paratype): Gerda-725, X3.0, USNM 46813; 3. R. gerdae (para- type): Gerda-725, x3.9, showing dissepiments, USNM 46813; 4-6. R. gerdae (calices of holotypic colony), x3.0, USNM 46812; 7. fi. gerdae (paratype): Gerda-725, x3.8, cross-section througli base, USNM 46813; 8. Rhizosmilia maculata: off Cozumel, Yucatan, 6.5 m, xl.5, showing dissepiments, USNM 46811. 220 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 79?10'W, 143-210 m, 3 August 1965; USNM 46814, paratype (1), Gerda-698, 26?28'N, 78?42'W, 163-329 ni, 22 July 1965; USNM 46S15, paratype (1), Gercla-701, 26?29'N, 78?40'W, 275-311 m, 22 July 1965; USNM 46816, paratypes (6 corallites), Gercla-702, 26?29'N, 78^40'W, 73-220 m, 22 July 1965; USNM 16138, paratypes (7 corallites), Albatross-2332, 23?10'38"N, 82?20'06"W, 285 m, 19 Jan. 1885; USNM 36364, paratypes (10 corallites), Albafross-23M, 23?10'42"N, 82nS'24"VV, 123 m, 19 Jan. 1885; USNM 10210, paratype (1), Alhatnm-2336, 23 ?10'4S"N, 82?18'52"W, 287 m, 19 Jan. 1885; USNM 36418, paratypes (14+ corallites), Albatross station unknown (off Havana, Cuba), 1885.?Other material: USNM 46817, 1 colony (4 coral- lites), Albatross station unknown (off Havana, Cuba), 1885; USNM 46818, 4 corallites, Caribbean Sea (no additional data). Description.?The colony forms phaceloid clumps by extratentacular budding from a common basal coenosteum. Corallites are cylindrical or slightly tapered at the base. The base of a corallite increases in diameter by adding exothecal dissepiments over raised costae as previously described for the genus. A typical corallitc> measures 12 X 10 mm in calicular diam- eter and 21 mm tall, although adult corallites vary from 7-17 mm in greater calicular diameter and may be up to 45 mm tall. Costae are usually well- defined only in the upper half of the corallum where they are equal, low, rounded ridges separated by equally shallow grooves. Very small granules cover the costae. Septa are arranged in 6 systems and 4-5 cycles. A corallite of 8-11 mm calicular diameter usually has a complete fourth cycle (48 septa), whereas, above 11 mm, pairs of S-, are common, but a complete fifth cycle is rare. Si are usually slightly larger than Sa, exsert, and have straight, vertical inner edges that do not reach the columella. The remaining cycles are progres- sively smaller and less exsert; Sr, are rudimentary with dentate inner edges. Low, blunt granules cover the septal faces. A large paliform lobe, compressed in the plane of the septum, occurs before each septum of the penultimate cycle and maintains its position there as described in the generic discussion. Each paliform lobe is separated from its respective septum by a deep, narrow notch and together they fomi a crown deeply set in the fossa. The columella is prominent and quite variable. It may be an elliptical, spongy mass, or linear, individuahzed pillars, or a .single lamella. Endothecal dissepiments aie abundant. Discussion.?R. gerdae is very similar to RhizosmiUa maculata (Pourtales, 1874) n. comb., particularly in its growth form and aspects of its paliform lobes, dissepiments (Plate 1, Fig. 8), costal roots, and columella. It may be distinguished by the smaller size of its corallites (none known to ex- ceed 15 mm in greater diameter), complete absence of Sc, absence of brown speckled pigmentation, and shallower fossa. Although they have overlapping VOLUME 91, NUMBER 1 221 depth ranges, R. gerdae is more typical of the deeper shelf, whereas R. maculata is found in shallower waters (3-161 m). R. maculata is described and illustrated in Cairns (1977) as Canjoplu/Uia maculata. EUimologii.?The specific name gerdae is given in honor of the University of Miami's H/V Gerda, al)oard wliich many of the type-specimens were collected. Type-locality.?Oit Bimini, Straits of Florida: 26?01'N, 79?10'W, 143- 210 m. Geographic distribution.?Insular side of Straits of Florida. Bathyrnetric range.?123-287 m (confirmed). Literature Cited Cairns, S. D. 1977. Stony corals. I. Caryophylliina and DendrophyUiina (Antliozoa: Scleractinia). Memoirs of the Hourglass Cruises .3(4): 29 pp, 2 pis. Durliaui, J. W. 1949. Ontogenetic stages of simple corals. Univ. Califoniia Publ., (Geol. Sci.) 28(6); 137-172, pis. 4r-S. Pourtales, L. F. 1874. Zoological results of the Hasslcr expedition. Deep-sea corals. Illustr. Cat. Mus. Comp. Zool. 8:33-50, pis. 6-10. . 1880. Report on the results of dredging ... by the U.S. Coast Survey steamer Blake. 6. Report on the corals and Antipatharians. Bull. Mus. Comp. Zool. 6(4): 95-120, pis. l-^. Vaughan, T. W., and J. W. Wells. 1943. Revision of the suborders, families, and genera of the Scleractinia. Geol. Soc. Amer., Spec. Pap. 44:1-363, pis. 1-51. Wells, J. -'/. 1947. Coral Studies. Part 5. A new Coenocyathus from Florida. Bull. Amer. Paleont. 31(123): 170-171, pi. 11. . 1972. Some shallow water ahermatypic corals from Bermuda. Postilla No. 156:1-10, 17 figs. Division of Biology and Living Resources, Rosenstiel School of Marine and Atmo.spheric Science, University of Miami, Miami, Florida 33149; Mail- ing address: Department of Invertebrate Zoology, National Museum of Natural History, Washington, D.C. 20560.