Terminonatator ponteixensis, a new elasmosaur (Reptilia; Sauropterygia) from the Upper Cretaceous of Saskatchewan

A new elasmosaur, Terminonatator ponteixensis, gen. et sp. nov., from the Upper Campanian Bearpaw Formation of southwestern Saskatchewan, Canada, is one of the youngest plesiosaurs from the Western Interior, and one of the few plesiosaurs for which detailed osteology of both skull and postcrania is available. The skull includes the upper side of the inner ear cavity and a median portion of the roof of the braincase. This taxon is distinguished from other elasmosaurs by a combination of several osteological characters variable among elasmosaurs, as well as the unique feature of a high and pointed coronoid process. Anomalous ossification is seen in the fused or pronged gastralia, development of tubercules in metacarpals, and healed fracture of the limb. The dorsal portion of the braincase is compared with other plesiosaurs, showing a variation in plesiosaur braincase morphology. Identity of carpal and tarsal elements is examined based on recent debates on the homology of mesopodials.