An Update on Mosasaurine (Reptilia; Squamata) Remains from the Hell Creek Formation, North Dakota, USA.

VAN VRANKEN, Nathan E; Independent Researcher, The Colony, TX. BOYD, Clint A; North Dakota Geological Survey, Bismarck, ND.

 Abstract

Mosasaurs are a group of well-known carnivorous marine reptiles that once swam the epeiric sea that flowed over the Great Plains region in North America during the Late Cretaceous. Both North and South Dakota have sparse records of mosasaurid occurrences after the deposition of the Campanian Pierre Shale Formation. The discovery of new fossil remains collected from within the Maastrichtian Breien Member of the Hell Creek Formation in North Dakota suggests that large-bodied (8m or longer) mosasaurids were still present in the region before the complete recession of the seaway. Based on fossil elements collected from a new locality, along with an assessment of other geologically young mosasaurid remains found in North America we can confirm the presence of a mosasaurine mosasaur. The focus of this research is to help further develop the body of understanding of the latest Cretaceous intercontinental mosasaurs and bolster the biodiversity found within the marine units of the Hell Creek Formation.