Szechuanosaurus

''Szechuanosaurus'' (" Szechuan lizard") is an extinct genus of carnivorous theropod dinosaur from the Late Jurassic. Fossils referred to the genus have been found in China, Asia in the Oxfordian-?Tithonian (Peng ''et al''., 2005). Its type species is based on several undiagnostic teeth from the Kuangyuan Series. Additional possible specimens of ''Szechuanosaurus'' were also reported from the Kalaza Formation, also located in China.

''Szechuanosaurus'' is at times regarded as a ''nomen dubium'' due to the lack of diagnostic features in the fossilized teeth upon which the genus is based. Although the fossils are too fragmentary for confident identification, ''Szechuanosaurus'' is often interpreted as a medium-sized allosaurid or perhaps a metriacanthosaurid, capable of reaching lengths of around 7.3 meters.

Discovery and species

Three species have been assigned to this genus over the years. The type species is ''Szechuanosaurus campi'', named by Yang Zhongjian ("Chung Chien Young") in 1942 for four isolated tooth specimens: IVPP V235, two partial teeth; IVPP V236, a partial tooth; IVPP V238, several tooth fragments; and IVPP V239, a single tooth. The teeth form a syntype series and were not found together. Also a very fragmentary skeleton, specimen UCMP 32102, was referred to the genus by Yang.Young, C.C., 1942, "Fossil vertebrates from Kuangyuan, N. Szechuan, China", ''Bulletin of the Geological Society of China'', 22: 293-309 Some of the teeth indicate a large body-size. These fossils, although possibly metriacanthosaurid, are now considered to be non-diagnostic, making ''S. campi'' a ''nomen dubium''.Brusatte, S. L., Benson, R. B. J., and Xu, X. 2010. "The evolution of large-bodied theropod dinosaurs during the Mesozoic in Asia". ''Journal of Iberian Geology'', 36: 275-296 The generic name refers to Szechuan. The specific name honours the American paleontologist Charles Lewis Camp who had discovered UCMP 32102.

A partial skeleton, CV 00214, was initially listed by Dong ''et al.'' (1978) in a faunal list as a new species of ''Szechuanosaurus'', ''Szechuanosaurus yandonensis''. At first, there was no description or illustration of it, making ''S. yandonensis'' at the time a ''nomen nudum''. Later, Dong Zhiming ''et alii'' (1983) described it, and assigned it to ''Szechuanosaurus campi'' The affinities of this skeleton are uncertain, and it has only been briefly described. Holtz ''et al''. (2004) included it in their phylogenetic analysis and found it to be the most basal tetanuran. This individual was a medium-sized theropod, with an ischium (a pelvic bone) of ; for comparison, an ischium of '' Piatnitzkysaurus'' estimated to weigh is long. In 2000, Daniel Chure referred the specimen to " Szechuanoraptor dongi", itself an invalid ''nomen ex dissertatione''.Chure, D.J. (2000) ''A new species of'' Allosaurus ''from the Morrison Formation of Dinosaur National Monument (UT–CO) and a revision of the theropod family Allosauridae''. Unpublished Ph.D. dissertation, Columbia University, New York Carrano, Benson & Sampson (2012) synonymized it with ''Yangchuanosaurus shangyouensis'' from the same formation.

The third species is ''Szechuanosaurus zigongensis'', named by Gao Yuhui in 1993 for an almost complete skeleton, specimen ZDM 9011.Gao, Y., 1993, "A new species of ''Szechuanosaurus'' from the Middle Jurassic of Dashanpu, Zigong, Sichuan", ''Vertebrata PalAsiatica'' 31(4): 308-314 It is an older species, from the Middle Jurassic, appearing to be distinct from the type species and therefore requires its own genus name. It was reassigned to ''Yangchuanosaurus'', as a ''Yangchuanosaurus zigongensis'', by Matthew Carrano, Roger Benson & Scott Sampson in 2012.

Notes

References

''Szechuanosaurus campi'' in The Theropod Database

{{Taxonbar, from=Q637535

Tetanurae
Dinosaur genera
Oxfordian dinosaurs
Taxa named by Yang Zhongjian
Fossil taxa described in 1942
Dinosaurs of China