Tricuspisaurus

Tricuspisaurus is an extinct genus of reptile originally described as a trilophosaurid;^[1] it was later considered likely to be a procolophonid,^[2][3][4] but recent analyses have affirmed the original classification.^[5] Fossils are known from the Ruthin Quarry in Glamorgan, Wales, one of several Late Triassic to Early Jurassic British fissure deposits. Like some trilophosaurs, it has an edentulous, or toothless beak. Tricuspisaurus gets its name from its heterodont dentition, which includes tricuspid teeth, or teeth with three cusps. The type species, T. thomasi, was named in 1957 along with the possible trilophosaur Variodens inopinatus from Somerset, England.^[1]

Tricuspisaurus Temporal range: Late Triassic, 205.6–201.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Clade:	Archosauromorpha
Clade:	†Allokotosauria
Order:	†Trilophosauria
Family:	†Trilophosauridae
Genus:	†Tricuspisaurus Robinson, 1957
Type species
†Tricuspisaurus thomasi Robinson, 1957

Although originally classified as a trilophosaur, Tricuspisaurus was reclassified as a procolophonid in 1993 by paleontologists Hans-Dieter Sues and Paul E. Olsen.^[2] This was due to similarities between its tricuspid teeth and those of the newly described procolophonid Xenodiphyodon. Along with Tricuspisaurus, Variodens and Trilophosaurus jacobsi were also considered to be procolophonids.^[3] More recently described cranial material from T. jacobsi indicates that it is still likely to be a trilophosaur.^[4][5]

References

1. Robinson, P.L. (1957). "An unusual sauropsid dentition". Zoological Journal of the Linnean Society. 43 (291): 283–293. doi:10.1111/j.1096-3642.1957.tb01554.x.
2. Sues, H.-D.; Olsen, P.E. (1993). "A new procolophonid and a new tetrapod of uncertain, possibly procolophonian affinities from the Upper Triassic of Virginia". Journal of Vertebrate Paleontology. 13 (3): 282–286. Bibcode:1993JVPal..13..282S. doi:10.1080/02724634.1993.10011510.
3. Fraser, N.C. (1994). "Assemblages of small tetrapods from British Late Triassic fissure deposits". In Fraser, N.C.; Sues, H.-D. (eds.). In the Shadow of the Dinosaurs: Early Mesozoic Tetrapods. Cambridge and New York: Cambridge University Press. pp. 214–225. ISBN 9780521458993.
4. Heckert, A.B.; Lucas, S.G.; Rinehart, L.F.; Spielmann, J.A.; Hunt, A.P.; Kahle, R. (2006). "Revision of the archosauromorph reptile Trilophosaurus, with a description of the first skull of Trilophosaurus jacobsi, from the Upper Triassic Chinle Group, West Texas, USA" (PDF). Palaeontology. 49 (3): 621–640. Bibcode:2006Palgy..49..621H. doi:10.1111/j.1475-4983.2006.00556.x.
5. Skinner, Matthew; Whiteside, David I.; Benton, Michael J. (2020). "Late Triassic island dwarfs? Terrestrial tetrapods of the Ruthin fissure (South Wales, UK) including a new genus of procolophonid". Proceedings of the Geologists' Association. 131 (5): 535–561. Bibcode:2020PrGA..131..535S. doi:10.1016/j.pgeola.2020.04.005. S2CID 221878712.

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