Thecodontosaurus

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Thecodontosaurus
Fossil range: Late Triassic

Life restoration of Thecodontosaurus antiquus

Kingdom:	Animalia
Phylum:	Chordata
Class:	Sauropsida
Superorder:	Dinosauria
Order:	Saurischia
Suborder:	Sauropodomorpha
Family:	Thecodontosauridae Lydekker, 1890
Genus:	Thecodontosaurus Riley & Stuchbury, 1836

Species

T. antiquus Morris, 1843 (type)

Thecodontosaurus ("socket-tooth lizard") is a genus of herbivorous dinosaur which lived during the late Triassic period Period (Norian and/or Rhaetian age). Its remains are known mostly from Triassic "fissure fillings" in South England and Wales. On average, it was 1.20 metres (4 ft) long, 0.3 metres (1 ft) tall, and weighed 11 kilograms (25 lb).

Thecodontosaurus had a rather short neck supporting a fairly large skull with quite big eyes. Its jaws contained many small- to medium-sized, serrated, leaf-shaped teeth. This dinosaur's hands and feet each had five digits, and the hands were long and rather narrow with an extended claw on each. This dinosaur's front limbs were much shorter than the legs, and its tail was much longer than the head, neck and body put together.

Although not actually the earliest member of the group, Thecodontosaurus is the most primitive well-known representative of the sauropodomorph dinosaurs. Originally it was included under the Prosauropoda (Upchurch 1998) but more recently it has been suggested that Thecodontosaurus and its relatives were prior to the prosauropod-sauropod split (Yates & Kitching 2003). New reconstructions show that its neck is proportionally shorter than in more advanced early sauropodomorphs.

The original type specimen of Thecodontosaurus was a victim of World War II bombings by the Germans. The remains of this dinosaur and other material related to it were destroyed in 1940. However, more remains have been found at a number of localities, including Bristol. Some of this new material pertains to a juvenile specimen that may belong to a distinct species, Thecodontosaurus caducus Yates, 2003. The dinosaur Agrosaurus macgillivrayi (Seeley, 1891), once thought to be from Australia, but more likely from England and misidentified, is probably synonymous with Thecodontosaurus antiquus (Vickers-Rich et al., 1999).

In 2007, a paper by Yates, Galton, and Kermack put forth the claim that Thecodontosaurus caducus belongs to a different genus, which they have named Pantydraco.

[edit] References

Upchurch, P. (1998). The phylogenetic relationships of sauropod dinosaurs. Zool. J. Linnean Soc. 124: 43–103.

Vickers-Rich, P., Rich, T.H., McNamara, G.C., & Milner, A. (1999). Agrosaurus: Australia's oldest dinosaur? Records of the Western Australian Museum Supplement 57: 191-200.

Yates, A. M. (2003). A new species of the primitive dinosaur Thecodontosaurus (Saurischia: Sauropodomorpha) and its implications for the systematics of early dinosaurs. Journal of Systematic Palaeontology 1(1): 1-42.

Yates, A.M. & Kitching, J. W. (2003). The earliest known sauropod dinosaur and the first steps towards sauropod locomotion. Proc. R. Soc. Lond.: B Biol Sci. 2003 Aug 22; 270(1525): 1753–8.

Galton, P.M., Yates, A.M., & Kermack, D. (2007). Pantydraco n. gen. for Thecodontosaurus caducus Yates, 2003, a basal sauropodomorph dinosaur from the Upper Triassic or Lower Jurassic of South Wales, UK. Neues Jahrbuch für GEologie und Paläontologie, abh., 243: 119-125.