Stokesosaurus

Stokesosaurus (meaning "Stokes' lizard") is a genus of small (around 3 to 4 meters in length) early tyrannosaur from the Late Jurassic period of Utah and England. It was named after Utah geologist William Lee Stokes.[1] Remains possibly referable to Stokesosaurus have been recovered from stratigraphic zone 2. of the Morrison Formation.[2]

The holotype (UUVP 2938) consists of a hip bone, originally thought to belong to the possible early tyrannosaur Iliosuchus,[3] as well as several vertebrae and a partial braincase.[4] Another ilium referred to this dinosaur[5] is lost but may actually belong to the related Aviatyrannis, and a premaxilla thought to belong to Iliosuchus[1] is actually from Tanycolagreus.

A second species, Stokesosaurus langhami, was described by Roger Benson in 2008 based on a partial skeleton. The skeleton consists of an "associated partial skeleton represented by a complete pelvis" as well as a partially complete leg, and neck, back, and tail vertebrae.[6] This second skeleton was discovered in 1984 in Dorset, was mentioned in several papers, but was not formally described until 2008. The new species was named in honor of Peter Langham, who collected the specimen. The new specimen was discovered in strata dating from the Tithonian, the final stage of the Late Jurassic, meaning the fossil is around 150 million years old.[6]

Stokesosaurus and Tanycolagreus are about the same size, and it is possible that the latter is a junior synonym of the former. However, the ilium (the best known element of Stokesosaurus) of Tanycolagreus has never been recovered, making direct comparison difficult.[7]