Abstract

In 1987, a Sino-Canadian expedition known as the Dinosaur Project (China – Canada – Alberta – Ex Terra) discovered a large theropod skeleton in the Upper Jurassic Shishugou Formation of the Junggar Basin in northwestern China. The well-preserved skeleton lacks much of the tail and most of the arms, but is otherwise nearly complete. The new genus and species, Sinraptor dongi, represents a poorly understood stage of theropod evolution, even though a related form, Megalosaurus, was the first dinosaur described and named (by W. Buckland in 1824). Sinraptor has a large pneumatopore in the jugal, a pronounced postorbital rugosity, a relatively long intertemporal bar in which the postorbital appears very short in lateral aspect, and a pneumatic palatine. It is more advanced than Piatnitzkysaurus from Argentina, less derived than Allosaurus, and shows its strongest similarities to Yangchuanosaurus. The preorbital skull length of Sinraptor is relatively longer than in Yangchuanosaurus, but the skull is relatively lower. A specimen from Sichuan recently described as "Yangchuanosaurus" hepingensis represents a second species of Sinraptor. Sinraptor and Yangchuanosaurus are united in a new family of theropods, the Sinraptoridae.

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