Caenagnathids (Theropoda, Oviraptorosauria) from the uppermost Maastrichtian of the Scollard Formation of Alberta, Canada

Abstract

Recent work has greatly improved our understanding of the diversity and paleobiogeography of caenagnathids in North America. However, the late Maastrichtian caenagnathid record remains poorly understood, with only two species established from this time interval. Here we describe three isolated elements of caenagnathids recovered from the base of the upper Maastrichtian portion of the Scollard Formation of Alberta, Canada. Two specimens, a metatarsal II and a pedal ungual, represent large-bodied species and are most similar to the same elements in Anzu wyliei (upper Maastrichtian Hell Creek Formation) and Caenagnathus collinsi (upper Campanian Dinosaur Park Formation). The third specimen, a pedal ungual from an immature individual, is most similar to Leptorhynchos gaddisi (upper Campanian Aguja Formation). Preservation of only isolated elements from the Scollard Formation and a scarcity of relevant comparative specimens from the upper Maastrichtian in general, hinders taxonomic assignment of these specimens to the genus level. Regardless, these specimens provide evidence for the widespread and northerly occurrence of caenagnathids, including large-bodied forms, in North America during the last one million years of the Cretaceous.