The Ceratopsian Dinosaurs and Associated Lower Vertebrates from the St. Mary River Formation (Maestrichtian) at Scabby Butte, Southern Alberta

Abstract

Scabby Butte, a limited exposure of late Cretaceous sediments in southern Alberta, Canada, is an important source for the large ceratopsian dinosaur Pachyrhinosaurus Sternberg. New cranial material confirms this taxon's place among short-faced ceratopsids, and circumstantial evidence suggests that it possessed a spiked frill reminiscent of Styracosaurus. Postcranial bones associated with Pachyrhinosaurus skulls in a bonebed deposit probably belong to the genus and indicate a massive body approaching Triceratops dimensions. Another ceratopsian, Anchiceratops, is sparsely represented.All classes of gnathostomes, except birds, are represented by fragmentary material at Scabby Butte. Of 21 lower vertebrate taxa, fourteen are new to the St. Mary River Formation (Squatirhina, Squatina, Amia, Belonostomus, Paralbula, Platacodon, Opisthotriton, Boremys, Plioplatecarpus, a tyrannosaur, a coelurosaur, an ornithomimid, Troödon, Edmontosaurus, Edmontonia).