Osteology and relationships of Chirostenotes pergracilis (Saurischia, Theropoda) from the Judith River (Oldman) Formation of Alberta, Canada

Abstract

A partial skeleton of a small theropod found in the Judith River Formation of Dinosaur Provincial Park (Alberta) shows that Chirostenotes pergracilis is the same animal as "Macrophalangia canadensis" and probably "Ornithomimus elegans." New information on the skeleton suggests that Chirostenotes is closely related to Elmisaurus and Oviraptor and that these animals are derived from dromaeosaurid stock. Both robust and gracile forms are known from Alberta, and it is suggested that these correspond to the two "species" of Caenagnathus and represent sexual dimorphism. Microvenator from the Lower Cretaceous of Montana may represent an early caenagnathid. Specializations in the pelvic girdle and hind limb may indicate wading habits.