284 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 13, NO. 3, 1993 teeth of Hypsognathus (Colbert, 1946:fig. 15) and of near Midlothian, Chesterfield County, Virginia. Lat. Tichvinskia from the Lower Triassic of Russia (Ivakh- 77040'15"N, long. 37027'45"W; Hallsboro 7.5 Minute nenko, 1979:fig. 3b), is interpreted as the more ante- Quadrangle. riorly placed tooth. Diagnosis--Type and only known species of the ge- The teeth have robust, transversely broadened, bi- nus as diagnosed above. cuspid crowns. It is difficult to ascertain the nature of Description--The tooth-bearing ramus of the den- tooth implantation; it appears to be ankylothecodont. tary is deep dorsoventrally but very narrow transverse- The maximum width of the tooth crown is at its base, ly, slightly increasing in width posteriorly. Its anterior from which it narrows uniformly toward the apices of and posterior ends are broken off. The labial surface the cusps, resulting in sloping sides of the crown. The is distinctly convex dorsoventrally, especially more two cusps are linked by a transverse ridge, which is posteriorly. The dentary fragment holds nine teeth, the rather sharp on the more posterior tooth but is weakly first of which is represented only by its base. A shallow developed on the more anterior tooth. Anterior and sulcus extends anteroposteriorly lingual to the tooth posterior to this ridge, there is a deep pocket or fossette, row. Judging from inspection of the broken ends of the which is bounded by a sharp cingular ridge on the side jaw fragment, implantation of the teeth appears to be opposite to the transverse ridge. The cusps have strong- ankylothecodont, although this remains to be verified ly fluted enamel. The teeth are tightly apposed. by dissection of additional material. The anterior six The transversely broadened tooth crowns with two teeth have anteroposteriorly aligned, transversely apical cusps linked by a transverse ridge support place- strongly compressed crowns with distinct apical ridges. ment of Gomphiosauridion in the Procolophonidae The first tooth was apparently long anteroposteriorly. (Huene, 1912; Gow, 1977a, b; Ivakhnenko, 1979; Car- The lingual surfaces of the anterior crowns are flattened roll and Lindsay, 1985), but it differs from other mem- and obliquely inclined (although these features may bers of this group in the presence of two deep fossettes, have been accentuated by wear). The crown of the sixth rather than one. The prominent fluting of the enamel tooth is less compressed transversely in occlusal view on the cusps is an additional diagnostic feature for than those of the preceding teeth. The posterior three Gomphiosauridion. Thelegnathus from the Lower or teeth have transversely broadened crowns, which in- Middle Triassic of South Africa also exhibits fluted crease in labiolingual width from the first to the last enamel on the more posterior "molariform" teeth (1.0 and 1.4 mm, respectively). Two shallow grooves (Gow, 1977a; Spencer, pers. comm.). extend anteroposteriorly and divide the occlusal sur- face of each posterior tooth into three cusps, the central ?PROCOLOPHONIA one of which is the largest (especially on the first tri- cuspid tooth). The apices of all cusps appear to be worn. Genus XENODIPHYODON,gen. nov. Discussion - Xenodiphyodon is so decidedly distinct Type Species--Xenodiphyodon petraios, sp. nov. that even its placement in a major group of tetrapods Diagnosis--Tooth-bearing ramus of dentary deep is difficult at present, but it appears to be most similar dorsoventrally but narrow transversely. Lower denti- to certain genera of Procolophonidae in the structure tion distinctly heterodont, with anteroposteriorly of its dentition. Its anterior teeth resemble the antero- aligned, transversely compressed anterior teeth and posteriorly aligned posterior teeth in the dentary and transversely broadened, tricuspid posterior teeth. maxilla of a new procolophonid from the Upper Tri- Etymology-Greek xenos, strange, Greek diphyes, assic Wolfville Formation of Nova Scotia, first re- double, twofold, and Greek odous (specifically the Io- ported by Baird and Take (1959) and currently under nian variant odon), tooth, in allusion to the presence study by Baird and Sues. Somewhat similar teeth also of two distinct tooth types. occur in Colognathus Case, 1928 from the Upper Tri- assic Dockum Group of Texas, a poorly known form that has been considered a procolophonid by some XENODIPHYODON sp. nov. PETRAIOS, authors (e.g., Murry, 1986) if it is, in fact, a tetrapod. (Fig. 2) The tricuspid posterior teeth of Xenodiphyodon Etymology - Greek petraios, of or belonging to a rock, closely resemble those of Trilophosaurus buettneri Case, from Greek petra, rock, also the etymological root for 1928 from the Upper Triassic Dockum Group of Texas the first name of the discoverer of the holotype, Peter and Tricuspisaurus thomasi Robinson, 1957 from the A. Kroehler. Upper Triassic fissure-fillings of Ruthin Quarry near Holotype--USNM 448631, incomplete right den- Cowbridge, Glamorgan (England). Although place- tary with nine teeth (Fig. 2). Collected by P. A. Kroeh- ment of Trilophosaurus buettneri in the Archosauro- ler on July 7, 1991. morpha is well corroborated by numerous cranial and Horizon and Locality -Tomahawk Member, Tur- postcranial synapomorphies (Gauthier, 1984), the tri- key Branch Formation, Newark Supergroup. Age: Late lophosaurid affinities of other taxa such as Tricuspi- Triassic (early to middle Carnian). USNM locality saurus are questionable. Reviewing both Robinson's 39981 (Tomahawk Locality), 0.16 km (0.1 miles) E of original material and more recently collected referred the eastern branch of Little Tomahawk Creek along specimens, Fraser (1986) argued that Tricuspisaurus is the northeastern side of Old Hundred Road (VA 652), a procolophonid. Some of the transversely broadened

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phonids with tricuspid teeth (Fraser, 1986), but more Jurassic boundary in South West Britain. Modern Ge- complete cranial material is needed to test this hy- ology 10:147-157. pothesis of relationships. Gauthier, J. A. 1984. A cladistic analysis of the higher systematic categories of the Diapsida. Unpublished Ph.D. dissertation, University of California, Berkeley, 564 pp. ACKNOWLEDGMENTS Gilmore, C. W. 1928. A new fossil reptile from the Triassic of New Jersey. Proceedings of the United States National We thank P. A. Kroehler and E. B. Sues for their Museum 73(7):1-8. enthusiastic help in the field. M. A. Parrish drew the Gow, C. E. 1977a. New procolophonids from the Triassic of specimens. H.-D. S. gratefully acknowledges discus- Cynognathus zone South Africa. Annals of the South sions with D. N. C. and P. all African Museum 72:109-124. Baird, Fraser, Spencer, 1977b. Tooth function and succession in the Tri- of whom also access to unpublished material granted assic reptile Procolophon trigoniceps. Palaeontology 20: and helpfully commented on a draft of the manuscript. 695-704. M. Morales (Museum of Northern Arizona) kindly ar- Huene, F. v. 1912. Die Cotylosaurier der Trias. Palaeon- ranged for the loan of specimens. This study forms tographica 59:69-102. part of a project supported by grants from the National Ivakhnenko, M. F. 1979. Permskiye i triasovyye proko- Geographic Society and the National Science Foun- lofony Russkoy platformy. Trudy Paleontologicheskogo dation (NSF EAR-90166179). Instituta, Akademiya Nauk SSSR 164:1-80. Murry, P. A. 1986. Vertebrate paleontology of the Dockum Group, western Texas and eastern New Mexico; pp. 109- LITERATURE CITED 137 in K. Padian (ed.), The Beginning of the Age of Dinosaurs: Faunal Change across the Triassic-Jurassic Baird, D. 1986. Some Upper Triassic reptiles, footprints, Boundary. Cambridge University Press, New York. and an amphibian from New Jersey. The Mosasaur 1987. New reptiles from the Upper Triassic Chinle 3:123-135. Formation of Arizona. Journal of Paleontology 61:773- and W. Take. 1959. Triassic reptiles from Nova 786. Scotia. Bulletin of the Geological Society of America 70: Olsen, P. E. 1988. Paleontology and paleoecology of the 1565-1566 (Abstract). Newark Supergroup (early Mesozoic, eastern North Carroll, R. L., E. S. Belt, D. L. Dineley, D. Baird, and D. C. America); pp. 185-230 in W. Manspeizer (ed.), Triassic- McGregor. 1972. Vertebrate Paleontology of Eastern Jurassic Rifting: Continental Breakup and the Origins Canada. Guidebook, Field Excursion A59, 24th Inter- of the Atlantic Ocean and Passive Margins. Elsevier, national Geological Congress, Montreal, Quebec, 113 Amsterdam pp. Reisz, R. R., and M. Laurin. 1991. Owenetta and the origin and W. Lindsay. 1985. Cranial anatomy of the of turtles. Nature 349:324-326. primitive reptile Procolophon. Canadian Journal of Earth Robinson, P. L. 1957. An unusual sauropsid dentition. Sciences 22:1571-1587. Journal of the Linnean Society, Zoology, 43:283-293. Case, E. C. 1928. Indications of a cotylosaur and of a new Sues, H.-D., D. Baird, and P. E. Olsen. In press. Rede- form of fish from the Triassic beds of Texas, with re- scription of Sphodrosaurus pennsylvanicus Colbert, 1960 marks on the Shinarump Conglomerate. Contributions (Reptilia) and a reassessment of its affinities. Annals of of the Museum of Paleontology, University of Michigan the Carnegie Museum. 3:1-14. - and P. E. Olsen. 1990. Triassic vertebrates of Gond- Colbert, E. H. 1946. Hypsognathus, a Triassic reptile from wanan aspect from the Richmond basin of Virginia. Sci- New Jersey. Bulletin of the American Museum of Nat- ence 249:1020-1023. ural History 86:225-274. 1960. A new Triassic procolophonid from Penn- sylvania. American Museum Novitates 2022:1-19. Received 9 April 1992; accepted 21 July 1992. Fraser, N. C. 1986. Terrestrial vertebrates at the Triassic- Corresponding Editor: R. J. Emry