ON CHIROSTENOTES, A LATE CRETACEOUS OVIRAPTOROSAUR (DINOSAURIOA, THEROPODA) FROM WESTERN NORTH-AMERICA

A previously unrecognized partial skeleton of Chirostenotes pergracili s Gilmore, 1924 from the Upper Cretaceous Horseshoe Canyon Formation o f Alberta (Canada) includes parts of the skull, much of the pelvic gir dle, and elements from all regions of the vertebral column. It provide s much new information concerning the skeletal structure of this unusu al theropod dinosaur. Close structural correspondence between the maxi lla of this specimen and the mandible of Caenagnathus collinsi R. M. S ternberg, 1940 indicates that the latter taxon should be considered a subjective junior synonym of Chirostenotes pergracilis. ''Ornithomimus '' elegans Parks, 1933 is probably also referable to Chirostenotes. Th e family-level taxon Elmisauridae Osmolska, 1981 is regarded as a subj ective junior synonym of Caenagnathidae R. M. Sternberg, 1940. The new ly recognized specimen of Chirostenotes pergracilis provides important new evidence for referring Caenagnathidae to Oviraptorosauria. Prelim inary phylogenetic analysis indicates a sister-group relationship betw een Oviraptorosauria and Therizinosauroidea.