Stokesosaurus clevelandi Madsen, 1974

Rauhut, Oliver W. M., 2003, The interrelationships and evolution of basal theropod dinosaurs, Special papers in palaeontology 69, pp. 1-213 : 27-28

Stokesosaurus clevelandi Madsen, 1974 ; metataxon

Age . Kimmeridgian-Tithonian.

Occurrence. Morrison Formation, Utah, USA.

Diagnosis. Differs from all other Late Jurassic theropods in the presence of a sharply defined vertical ridge on the ilium above the acetabulum.

Remarks. Although Stokesosaurus clevelandi is based only on an isolated ilium from the Cleveland Lloyd Quarry in the Morrison Formation of Utah ( Madsen 1974), the specimen is distinct from all other Jurassic theropods. In the original description, Madsen (1974) also referred a premaxilla to the same species, and just recently, Chure and Madsen (1998) described a braincase from the type locality as IStokesosaurus . Although the braincase in particular may well be referable to Stokesosaurus , this assignment is not accepted here, since there is no information about the association of these remains, and the Cleveland Lloyd Quarry has yielded thousands of theropod bones of at least four different species (Chure and Madsen 1998).

Despite its fragmentary nature, Stokesosaurus clevelandi is of considerable interest since the type ilium and referred ilia ( Madsen 1974) show many similarities to tyrannosaurids, a group that is otherwise only known from the Cretaceous. Therefore, Stokesosaurus is included in the analysis, although only a few characters can be coded for this taxon.