Chungkingosaurus

''Chungkingosaurus'', meaning "Chongqing Lizard", is a rather controversial genus of herbivorous dinosaur from the Late Jurassic Upper Shaximiao Formation in what is now China. It is a member of the Stegosauria. It is also a quadruped dinosaur.

Description

According to Dong e.a. the ''Chungkingosaurus jiangbeiensis'' holotype was one of the smallest stegosaurs with a length of less than four metres, even though it was apparently an adult, judging by the ossification of the sacrum. ''Chungkingosaurus'' sp. 1 was estimated at five metres; ''Chungkingosaurus'' sp. 2 was seen as longer than five metres. Dong e.a. indicated that ''Chungkingosaurus'' strongly resembled ''Tuojiangosaurus'', found in the same formation, in many anatomical details. ''Chungkingosaurus'' was different in its smaller size, deeper snout and front lower jaws (resulting in a relatively high and narrow skull), and non-overlapping teeth with less pronounced denticles.

''Chungkingosaurus'' probably possessed two rows of plates and spikes on its back, which were arranged in pairs, but the total number is unknown. A skeleton model in the Chongqing Municipal museum shows fourteen pairs of plates. This model also has two pairs of tail spikes. The plates of ''Chungkingosaurus'' have a thickened middle section, as if they were modified spikes. The plates resemble those of ''Tuojiangosaurus''. The form of the thagomizer, the tail end spikes used as a defensive weapon, is only known from specimen CV 00208. It preserves two pairs of obliquely vertical, rather stout, spikes. Dong et al. reported that a third pair to the front of these was originally present but lost during the excavation. A unique feature is the presence of an additional pair at the very tail end, consisting of long thin spikes oriented almost horizontally and obliquely to the sides and rear in top view. Paul described this kind of thagomizer as a "pin-cushion array". The thagomizer of ''Tuojiangosaurus'' is not known from articulated remains.

Discovery and species

Fossils of ''Chungkingosaurus'' were found near Chongqing, China, from 1977 onwards. The type species, ''Chungkingosaurus jiangbeiensis'', was named and described by Dong Zhiming, Zhou Shiwu, and Zhang Yihong in 1983. The generic name refers to Chongqing in Sichuan. The specific name refers to the district of Jiangbei.Z. Dong, S. Zhou, and Y. Zhang, 1983, " inosaurs from the Jurassic of Sichuan. ''Palaeontologia Sinica, New Series C'', 162(23): 1-136

The holotype, CV 00206, was found in the Chunking Group of the Upper Shaximiao Formation. It consists of a partial skeleton, containing the snout, the front of the lower jaws, ten dorsal vertebrae, a pelvis with sacrum, a series of twenty-three tail vertebrae, the lower end of a humerus, three metacarpals, both thighbones and shinbones and five back plates.

Dong e.a. in 1983 described three additional species. These were not separately named but identified as ''Chungkingosaurus'' sp. 1–3. ''Chungkingosaurus'' sp. 1 was based on specimen CV 00207, a pelvis with sacrum. The next species, ''Chungkingosaurus'' sp. 2, was based on specimen CV 00205, a partial skeleton. The last species, ''Chungkingosaurus'' sp. 3, was based on specimen CV 00208, a series of ten vertebrae of a tail end with an articulated thagomizer. In 2014, Roman Ulansky named CV 00205 ''Chungkingosaurus giganticus'', and CV 00207 ''Chungkingosaurus magnus''. Peter Malcolm Galton and Kenneth Carpenter later identified both as ''nomina dubia'', referring both to ''C. jiangbeiensis''.Galton, Peter M. & Carpenter, Kenneth, 2016, "The plated dinosaur ''Stegosaurus longispinus'' Gilmore, 1914 (Dinosauria: Ornithischia; Upper Jurassic, western USA), type species of ''Alcovasaurus'' n. gen.", ''Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen'' 279(2): 185-208

In 2006, Susannah Maidment and Wei Guangbiao considered ''Chungkingosaurus'' a valid genus, even though much of the material could no longer be localised. Specimen CV 00207 was by them no longer referred to ''Chungkingosaurus''.S. C. R. Maidment and G. Wei, 2006, "A review of the Late Jurassic stegosaurs (Dinosauria, Stegosauria) from the People's Republic of China", ''Geological Magazine'' 143(5): 621-634 However, Gregory S. Paul in 2010 suggested that ''Chungkingosaurus'' was the juvenile of ''Tuojiangosaurus''.Paul, G.S., 2010, ''The Princeton Field Guide to Dinosaurs'', Princeton University Press p. 221

Classification

''Chungkingosaurus'' was in 1983 by Dong e.a. placed in the Stegosaurinae. In 2006 Maidment & Wei considered it a basal member of the Stegosauria. In 2008 Maidment e.a. assigned it to the Huayangosauridae.S.C.R. Maidment, D.B. Norman, P.M. Barrett and P. Upchurch, 2008, "Systematics and phylogeny of Stegosauria (Dinosauria: Ornithischia)", ''Journal of Systematic Palaeontology'' 6(4): 367-407

Paleobiology

Like all stegosaurs, ''Chungkingosaurus'' was a herbivore. ''Chungkingosaurus'' is thought to have coexisted with large plant-eaters and stegosaurids such as ''Chialingosaurus'', ''Tuojiangosaurus'', ''Mamenchisaurus'', and ''Omeisaurus''. It may have also been preyed upon by theropods such as ''Yangchuanosaurus''.

See also

* Timeline of stegosaur research

References

External links

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{{Taxonbar, from=Q138023

Stegosauria
Dinosaur genera
Oxfordian dinosaurs
Shaximiao Formation
Fossil taxa described in 1983
Taxa named by Dong Zhiming
Dinosaurs of China