Stokesosaurus clevelandi, Madsen, 1974

Holtz, TR jr., 2004, Tyrannosauroidea, The Dinosauria, University of California Press, pp. 111-136 : 8

Stokesosaurus clevelandi

is based on an ilium from the Cleveland-Lloyd Quarry of the Kimmeridgian Morrison Formation of Utah ( fig. 5.23; Madsen 1975). Additional material includes a premaxilla (Madsen 1974) and a braincase (Chure and Madsen 1998), also from the Cleveland-Lloyd Quarry of the Kimmeridgian; another ilium from the Morrison of South Dakota (Foster and Chure 2000); and an ilium more closely resembling the South Dakota material than that from the Kimmeridgian Guimarota Coal Mine of Portugal (Rauhut 2000b). The latter in fact may belong to a separate basal tyrannosauroid genus (Rauhut, pers. comm.). Unfortunately, these associations are problematic and circumstantial. Stokesosaurus was a small dinosaur, the 22 cm long ilium suggesting an animal only 2–3 m long. Madsen provisionally referred it to Tyrannosauridae because of the presence of a single midline iliac crest rising dorsally from the supracetabular crest and incipient development of a ventral hooklike projection and medial support of the preacetabular blade. As in tyrannosaurids, the ventral ramus of the premaxilla is much deeper dorsoventrally than it is long proximodistally. The braincase is reminiscent of tyrannosaurids in the presence of a deep sinus on the ventral surface of the basisphenoid, and it is reminiscent of advanced tyrannosaurids in the small size of the basal tubera. The braincase also resembles that of the coelurosaur Itemirus medullaris , a taxon of uncertain affinities, in the presence of deep pockets on the lateral surface of the basipterygoid processes. The teeth of the premaxilla differ from those of tyrannosaurids in possessing a serrated carina along the mesial surface and lacking the buccolingual-oriented tooth arcade. However, premaxillary teeth of the tyrannosauroid U-shaped cross section are known from both the Morrison Formation (Bakker 1998a, 1998b; there considered dromaeosaurid teeth) and the Guimarota Coal Mine (Zinke 1998; Rauhut 2000b); these may come from the same taxa as the ilia, or they may indicate a different taxon.