Evolution and Diversity of Ornithomimid Dinosaurs in the Upper Cretaceous Belly River Group of Alberta

Ornithomimids from the Upper Cretaceous Belly River Group are among the best known theropods from these deposits, but questions remain concerning the oldest definitive occurrence of these dinosaurs in Alberta, as well as the taxonomic diversity of the articulated material. A partial skeleton is described and removed from Struthiomimus altus as the holotype of a new taxon. At least three ornithomimid taxa were roughly contemporaneous in the lower Dinosaur Park Formation. A reevaluation of isolated elements rejects reports of this clade from the Santonian Milk River Formation. The oldest Albertan material definitively referable to Ornithomimidae is from the lower Oldman Formation, and it is proposed that derived ornithomimids migrated into Laramidia during the Campanian. Characters considered diagnostic of the Chinese taxon Qiupalong are reported in material from the Belly River Group, supporting a close relationship between Asian and Albertan ornithomimids, and possibly a more complex palaeobiogeographic history than previously hypothesized.