PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 113(3):590-595. 2000. A new species of Tethocyathus (Cnidaria: Anthozoa: Scleractinia: Caryophylliidae), a trans-isthmian azooxanthellate species Patricia Lattig and Stephen D. Cairns (PL) Institute de Investigaciones Marinas y Costeras, A. A. 10-16, Cerro Punta de Betin, Santa Marta, Colombia; (SDC) Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560-0163, U.S.A. Abstract. — A new species of Tethocyathus is described, T. prahli, charac- terized by having a tympaniform corallum shape and no fossa. Specimens were found living at 310 m in the Colombian Caribbean, 303-333 m at Cocos Island (Pacific Costa Rica), and from the early Pleistocene of Pacific Panama, sug- gesting a relictual distribution of a previously more widespread species. Teth- ocyathus prahli is probably unique among the Scleractinia in having a non- cosmopolitan trans-isthmian distribution. The diagnosis of the genus Tethocy- athus is emended to conform more closely to that of the type species. The discovery of an undescribed species of Tethocyathus from the Colombian Carib- bean and the same species from the Pleis- tocene of Pacific Panama raised interesting zoogeographic questions. In the course of writing the paper, several more specimens were discovered from the Recent of Cocos Island, reinforcing our zoogeographic inter- pretation, i.e., that living T. prahli represent a trans-isthmian relictual distribution of a moderately shallow-water azooxanthellate species that was more widely and continu- ously distributed in the early Pliocene of both ocean realms. It is one of the very few scleractinian corals to have an trans-isth- mian distribution in relatively shallow wa- ter. Abbreviations BID: Banco Interamericano de Desarrollo. COLCIENCIAS: Instituto Colombian© para el desarrollo de la Ciencia y la Tec- nologia, Francisco Jose de Caldas. H:D: Ratio of height to maximum cali- cular diameter of a corallum. INVEMAR: Instituto de Investigaciones Marinas y Costeras "Jose Benito Vives de Andreis" (Santa Marta, Colombia). SEM: Scanning Electron Microscope. STRI: Smithsonian Tropical Research In- stitute, Panama. USNM: United States National Museum, Washington, DC (now the National Muse- um of Natural History). Sx, C^, P^: cycle of septa, costae or pali, respectively, designated by numerical sub- script. S^ > Syi in the context of a septal for- mula, septa of cycle x are wider than those of cycle y. Methods Colombian specimens were collected us- ing a botton trawl of 9 by 1 m in aperture and 16 m length during INVEMAR Macro Fauna cruise 2 (Dec 1998). Pleistocene cor- als were collected as part of the Panama Paleontology Project. The Cocos Island specimens were collected on the Johnson- Sea-Link Galapagos/Cocos Islands Expedi- tion of 1986, sponsored by the Harbor Branch Oceanographic Institute. The holotype is deposited at INVEMAR, VOLUME 113, NUMBER 3 591 paratypes at the USNM and ENVEMAR Paratype images were taken at the USNM using SEM; other images were obtained and processed using methods described by Reyes and Navas (in press). Systematics Order Scleractinia Bourne, 1900 Suborder Caryophylliina Vaughan and Wells, 1943 Family Caryophylliidae Dana, 1846 Genus Tethocyathus Kiihn, 1933 Diagnosis {emended). — Corallum soli- tary, tympaniform to subcyclindrical; at- tached through a polycyclic base. Septothe- ca costate, but covered with tectura. Pali- form lobes before first cycle of septa; dis- crete pali before all but first and last cycle of septa. Columella papillose. Type species. — Thecocyathus microphyl- lus Reuss, 1871, by original designation. Remarks. — The emended diagnosis of Tethocyathus is narrower than that given by Cairns (1979) in that it requires a polycyclic base and a thecal tectura (sensu Stolarski 1995 and Roniewicz & Stolarski 1999), both characters found in the type species. Of the three Recent western Atlantic spe- cies placed in this genus by Cairns (1979), only one fulfills these requirements: T. cy- lindraceus (Pourtales, 1 868). The other two species, T. recurvatus (Pourtales, 1878) and T. variabilis Cairns, 1979, have monocyclic bases. Two additional species exist in the western Pacific: T. virgatus (Alcock, 1902) and T. minor (Gardiner, 1899). The genus is very similar to Trochocyathus, differing in having a polycyclic base, a relatively squat corallum, and tectura-covered theca. The first cycle of entosepta (i.e., S,) of Tethocyathus may give off one or two crowns of paliform lobes, pali being found before the succeeding entoseptum. The di- agnostic character for Trochocyathus and Tethocyathus "pali before all but the last cycle of septa" (Vaughan & Wells 1943: 205-206, Wells 1956: F423) does not dis- tinguish pali from paliform lobes; therefore. we propose the diagnostic character be changed to: paliform lobes before first cycle of septa and pali before all but first and last cycles of septa. Tethocyathus prahli, new species Fig. 1 Description. — Corallum tympaniform (H:D usually < 0.5) and firmly attached by an expanded base. Polycyclic base contains up to 5 visible concentric thecal rings: counting from the center of the holotype, rings 2, 3, 4 and 5 measure 1.12 mm, 1.92 mm, 2.42 mm and 2.97 mm in diameter, respectively. Initial ring can not be seen from above because it is covered by the col- umella; however, in other coralla the first ring is about 0.7 mm in diameter. Calice round to elliptical; calicular edge slightly serrate. Holotype measures 8.1 by 7.7 mm in calicular diameter and 2.5-3.7 mm in height (H:D = 0.46). Theca (tectura) smooth and bears scalloped growth lines. Inner costae (i.e., those not yet encircled by a thecal ring) thin, ridged, and not granular; outer costae (i.e., those occurring on surface of outermost thecal ring) broader and gran- ular. C,_3 equal in size; C4 thinner. Septa hexamerally arranged in 4 cycles according to the formula: S1-S2 > S4 > S3. One paratype (i.e., the complete fossil and largest specimen, calicular diameter 13.8 by 12.0 mm, height 4.5 mm, H:D - 0.33: Fig. Id) has 54 septa due to the pres- ence of an extra half-system. S, and S2 equal in size and extend 0.75 to columella; each S, bears a small paliform lobe and each S2 bears a small palus. P|_2 small (0.34 mm wide) and occur closest to the colu- mella; only one Pj is wider (0.55 mm) than the others. S3 slightly smaller or equal in width to S4, extend 2/3 width of S,_2, and bear a large pali. P3 3 times wider (0.9 mm) than P,_2, and are recessed from columella. Therefore, two palar crowns are formed: the inner crown formed by 6 paliform lobes (P,) and 6 pali (Pj), and an outer crown of 12 P3. S4 fuse by their axial edges to adja- 592 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON a Fig. 1, a-d. Tethocyathus prahli. a, c. Recent paratype from Colombia, USNM 100469: a, stereo view of calice; c, oblique calicular view, b, stereo calicular view of holotype. d. Large paratype, Panama Paleontology Project site 148, USNM 95547, calicular view. VOLUME 113, NUMBER 3 593 cent S3 or P3. Inner edges of S,, S2 and S4 slightly sinuous; axial edges of S3 more sin- uous. Septal granules numerous, large, and blunt. Fossa very shallow to non extant. Colu- mella formed of fused papillae: massive and granular, appearing to incorporate part of the P,. Each P,_2 of fossil corallum have 2 or 3 lobes that extend and fuse to colu- mella. Discussion. — Tethocyathus prahli is quite similar to the type species, T. micro- phyllus, differing from it primarily in shape. Tethocyathus prahli has a lower, tympani- form corallum (the H:D ratio of T. prahli being between 0.3-0.5), whereas that of T. microphyllus is often above 2 and up to 3, i.e., subcylindrical. T. prahli also appears to have a larger corallum. Tethocyathus mi- crophyllus was most recently described and illustrated by Stolarski (1991). It is known from the Middle Miocene (Badenian) of Poland, Moravia, France, and Morocco. Several voucher specimens from Poland are deposited at the NMNH (USNM 86810 and 96496). Tethocyathus prahli also differs from T. cylindraceus (Pourtales, 1868) in shape, the latter species being ceratoid to subcylindr- ical, with a H:D usually over 1. Tethocy- athus cylindraceus also differs in having a shallow fossa and in having a very thick theca. It is known from the Caribbean (Straits of Florida, Jamaica, Barbados) at 183-649 m (Cairns 2000) and from north- eastern New Zealand (Cairns 1995). The presence of purportedly the same species in two ocean systems (i.e., the Pleis- tocene of the eastern Pacific and the Recent of the Caribbean) that have been separated for 3.6—3.5 million years (Coates et al. 1992, Collins 1993), suggests both an evo- lutionary stasis of that species and the ex- istence of that species in both oceanic realms (i.e., the Gatunian Province) before the closure of the isthmus. Indeed, Collins et al. (1996) logically argue that a deep- water species, such as T. prahli, would have been restricted from a trans-isthmian dis- persal since at least 5.3 Ma. Petuch (1981, 1988:156), based on Neogene and Recent moUusk distributions, has shown there to be several relict pockets within the Caribbean, these faunas containing genera or species surviving from an earlier widespread Late Miocene to Pliocene Gatunian distribution that covered the eastern Pacific and Carib- bean regions. One of these relict refugia, which he calls the "Venezuelan Secondary Relict Pocket", contains several mollusk taxa previously thought to be extinct, and appearing "to be most strongly under the influence of temporal stasis". The type lo- cality of T. prahli lies within this region. We therefore suggest that T. prahli existed in the Gatunian Province in both the eastern Pacific and Caribbean in the early Pliocene about 5.3 Ma, freely communicating across the future land bridge when there was still a channel of 150-200 m (Colhns et al. 1996). Between 5.3 and 3.5 Ma the genetic exchange was terminated due to the shal- lowing of the sill depth between the oceans. Tethocyathus prahli persisted to the Recent (at Cocos Island) and is documented from the early Pleistocene on the continental margin of the eastern Pacific (Panama), as well as surviving to the Recent in a relictual pocket off Colombia. However, based on so few specimens and the apparent lengthy isolation of the Atlantic and Pacific popu- lations of this purported trans-isthmian spe- cies, it is not unreasonable to assume that the type material might represent a cognate species pair or components of a subspecies pair. No reef corals are known to have a trans- isthmian distribution; however, at least sev- en azooxanthellate species occur in the Ca- ribbean and eastern Pacific (Cairns et al. 1999). But, all of these species are cosmo- politan in distribution and occur at much greater depths than T. prahli. Another two azooxanthellate species appear to have a trans-isthmian distribution: Madracis phar- ensis and M. asperula. Both species are well known from both sides of the North Atlantic, and have been tentatively reported 594 PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON from relatively shallow water (i.e., 16—343 m) from the eastern Pacific (i.e., Nazca Ridge, Chile; Galapagos; Colombia; Rocas Alijos; and Baja California), these occur- rences reviewed by Bonilla et al. (1995). However, there is doubt about the identity of these two species with the Atlantic forms, the Pacific specimens always being reported as Madracis sp. cf. M. pharensis. Thus, T. prahli and perhaps two species of Madracis constitute the only records of non-cosmopolitan Scleractinia with a trans- isthmian distribution. Etymology. — This species is named in honor of Henry Von Prahl (1949-1989), who made significant contributions to the knowledge of Colombian corals (Ramos & Lemaitre 1991). Types. — Holotype: INVEMAR Macro Fauna cruise 2, sta. 49, INVEMAR-COR 241. Paratypes: INVEMAR Macro Fauna cruise 2, sta. 49, 1 SEM stub, USNM 10046, and one corallum deposited at IN- VEMAR-COR 242. Johnson-Sea-Link I- 1943 (5°26'04"N, 87°07'59"W), Cocos Is- land, Costa Rica, 303-333 m, 2 Dec 1986, USNM 84868. Panama Paleontology Pro- ject site 047, 3 fragments, USNM 95546: eastern coast of Punta Burica, Pacific Pan- ama (8°11'24.0"N, 82°52'34.1"W), 1 km south of supertanker dock, 16 Jan 1986 (Charco Azul Group, Armuelles Formation, early Pleistocene). Panama Paleontology Project site 148, 1 complete specimen, USNM 95547: eastern coast of Punta Bur- ica, Pacific Panama (8°1 1'20.4"N, 82°52'33.5"W), near Q. Melliza, 21 Feb 1987 (Charco Azul Group, Armuelles For- mation, early Pleistocene). Type locality: INVEMAR Macro Fauna project, sta. 49: 1 1°05.26'-1 r05.12'N; 75°15.33'-75°15.74'W, off Bocas de Ceni- za, Magdalena, Colombian Caribbean, 310 m. Distribution and age. — Recent: known only from type locality off Colombia and Cocos Island (Costa Rica); 303-333 m. Fossil: early Pleistocene (Armuelles For- mation, 1.7—1.5 Ma) of Punta Burica, Pa- cific Panama. Acknowledgments We thank INVEMAR, and the Colom- bian Ministry of the Environment for sup- port of project number 2105-13-079-97, in collaboration with COLCIENCIAS and BID. The fossil corals were collected by the Panama Paleontology Project, funded by the National Science Foundation, STRI, the National Geographic Society, and the Ku- gler Fund, Basel. We also thank J. Stolarski (Instytut Paleobiologii PAN, Warsaw) for taking the SEM images and for helpful dis- cussions. Javier Reyes (INVEMAR, Co- lombia) produced the figures. This paper is Contribution No. 641 of the Instituto de In- vestigaciones Marinas y Costeras "Jose Be- nito Vives de Andreis" (Santa Marta, Co- lombia). Literature Cited Bonilla, H. R., E. M. Olguin, & G. A. Reyna. 1995. First record of Madracis sp. cf. 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