Stokesosaurus

The holotype of Stokesosaurus cleveland landi, a left ilium.

• Utah, North America ( Morrison Formation )

• Stokesosaurus cleveland landi

Stokesosaurus is a genus theropod dinosaurs and early representatives of Tyrannosauroidea, who lived during the Late Jurassic (Lower Tithonian ) in North America. Like all theropods, it was a bipedal carnivore; with an estimated body length between 2.5 to 4 meters, it was a smaller representative of the Tyrannosauroidea. Currently, can be safely assigned to this genus, only two ilia ( Ilia ) derived from the Morrison Formation of the U.S. state of Utah. Further findings of this genus have been attributed once, they belong to Stokesosaurus but has since been doubted or discarded. 2008 Stokesosaurus langhami a second type addition to the type species Stokesosaurus cleveland landi has been described, but this was in 2012 as an independent genus, Juratyrant, neubeschrieben.

Features

The ilium ( holotype specimen ) is about 22 cm long, which, according to Madsen ( 1974) points to a relatively small theropods, which reached no more than 4 meter body length. Paul ( 2010) estimated the body length, meanwhile, to 2.5 meters and the weight to 60 kg .. From related genera can be the ilium by a number of unique features ( autapomorphies ) differ: So this bone shows a semi-oval in side view outline; also was in before the acetabular cup ( acetabulum ) has a thin notch, whereas on the acetabulum extending a vertically oriented, distinct ridge.

Fund and discovery history

Since 1960, the geologist William Lee Stokes and his assistant James Madsen conducted excavations at the Cleveland -Lloyd Dinosaur Quarry. Among the finds were located next to thousands of bones of the theropod Allosaurus also the remains of previously unknown species. Thus, the new genus and species Stokesosaurus cleveland landi 1974 by James Madsen based on a left iliac ( holotype, specimen number UUVP 2938 ) and a left ilium and a Zwischenkieferbein was first described. The name honors William Lee Stokes for his work at the Cleveland -Lloyd Dinosaur Quarry, the species name includes the city of Cleveland in Utah. The Zwischenkieferbein in 2005 the genus Tanycolagreus attributed to Benson (2008 ) suggests, however, that it actually belongs to a Ceratosauria.

Since the initial description several other fossils of the genus have been assigned. Thus even a small, right ilium from the Wonderland quarry in South Dakota that has gone lost, however, and probably can not be attributed Stokesosaurus. Britt (1991 ) wrote Stokesosaurus provisionally to various vertebrae; Chure and Madsen ( 1998), meanwhile, assigned the genus to an isolated discovered skull. According to other researchers, however, are no common features with the Stokesosaurus - type fossils, which is why these associations were not justified.

A second type, Stokesosaurus langhami was described by Roger Benson in 2008 based on a partial skeleton. From this skeleton, which was discovered by Peter Langham found in 1984 in Dorset (England ), parts of the pelvis, sacrum, several vertebrae and the upper and lower leg are obtained. However, a recent study from 2012 describes this species as a new genus, Juratyrant.