A New Pachyrhinosaurus-Like Ceratopsid from the Upper Dinosaur Park Formation (Late Campanian) of Southern Alberta, Canada

摘要

IN 2001, AN ALMOST complete, but disarticulated, adultsized centrosaurine ceratopsid (TMP 2002.76.1) with a pachystotic nasal boss and deeply excavated bosses over the orbits on each postorbital was collected from the transgressive Dinosaur Park Formation (DPF) at Dinosaur Provincial Park (DPP) near Iddesleigh, Alberta. Surficial bone texture indicates that the specimen was an old, mature individual. Pathological deformations are present in the anterior parietal bar and in many of the phalanges. Unfortunately, the typically diagnostic posterior parietal was not recovered, hindering a definitive identification of the specimen. A restricted phylogenetic analysis of Centrosaurinae produced an unresolved trichotomy of (TMP 2002.76.1 + Achelousaurus + Pachyrhinosaurus). TMP 2002.76.1 occurs near the top of the DPF in a stacked channel succession that cuts out the lowest coal of the 15 m thick Lethbridge Coal Zone. Dates from bentonites that bracket this interval suggest an age of 75.1 Ma, making TMP 2002.76.1 the first occurrence of a pachyrhinosaur ceratopsid in the fossil record.