A New Polycotylid Specimen from the Bearpaw Shale of Montana

Abstract

A new polycotylid specimen from the Upper Cretaceous (Campanian-Maastrichtian) Bearpaw Formation of Northeastern Montana is described based on a partial, articulate skeleton. This specimen becomes only the second polycotylid described from the Bearpaw Shale, the last occurrence of polycotylids in North America. Preparation of this fossil specimen has revealed an ontologically mature adult skeleton that includes the left rear paddle, another partial paddle, pelvic bones, rib cage, and vertebral column, including nine cervical vertebrae. Ongoing sediment analysis hopes to provide critical dating information for such an exciting time in polycotylid evolution.