Pachysuchus

Pachysuchus is a dubious extinct genus of basal sauropodomorph dinosaur from the Early Jurassic of China.

Pachysuchus Temporal range: Early Jurassic, 196.5–189.6 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	Saurischia
Clade:	†Sauropodomorpha
Genus:	†Pachysuchus Young, 1951
Type species
†Pachysuchus imperfectus Young, 1951

Pachysuchus is known from a poorly preserved partial rostrum that was described from the Lower Lufeng Series in Yunnan by paleontologist Yang Zhongjian ("C.C. Young") in 1951.^[1] The type species is Pachysuchus imperfectus. The generic name translates as "thick crocodile"; the specific name means "imperfect" in Latin. Young identified the rostrum as that of a phytosaur, a long-snouted crocodile-like crurotarsan. Phytosaurs were common in the Triassic, but none are otherwise known from the Jurassic. They are thought to have gone extinct during the Triassic-Jurassic extinction event. The rostrum from which Young described the specimen had since been lost, and his first description of the genus had been questioned.^[2] The poor preservation of the specimen and its presence in Jurassic beds makes it doubtful that Pachysuchus is a phytosaur.^[3] Paul M. Barrett and Xu Xing (2012) relocated the holotype of P. imperfectus, specimen IVPP V 40, and identified it as actually belonging to a taxonomically indeterminate basal sauropodomorph. According to Barrett and Xu, the holotype of Pachysuchus "does not bear any unique features or a unique character combination"; it differs from rostra of other Early Jurassic Chinese sauropodomorphs, but it cannot be ruled out that the differences are caused by its poor preservation, making it a nomen dubium.^[4]

References

1. Young, C.C., 1951, "The Lufeng saurischian fauna in China", Palaeontologia Sinica, New Series C, 13: 1-96
2. Padian, K. (1989). "Did "thecodontians" survive the Triassic?". In Lucas, S.G.; Hunt, A.P. (eds.). Dawn of the Age of Dinosaurs in the American Southwest. Albuquerque: New Mexico Museum of Natural History. pp. 401–414.
3. Sun, A.-L.; Cui, K.H. (1986). "A brief introduction to the Lower Lufeng saurischian fauna (Lower Jurassic, Lufeng, Yunnan, People's Republic of China)". In Padian, K. (ed.). The Beginning of the Age of Dinosaurs: Faunal Change Across the Triassic-Jurassic Boundary. New York: Cambridge University Press. pp. 275–278.
4. Paul M. Barrett and Xu Xing (2012). "The enigmatic reptile Pachysuchus imperfectus Young, 1951 from the Lower Lufeng Formation (Lower Jurassic) of Yunnan, China" (PDF). Vertebrata PalAsiatica. 50 (2): 151–159.

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