Scanning electron microscope analysis of enamel microstructure in a Polycotylid (Plesiosauria) from the Pierre Shale Group, South Dakota, U.S.A.

The teeth of polycotylid plesiosaurs are generally simple, cone shaped, non-serrated and only slightly recurved without distinct carinae. The surface of crowns are characterized by a series of vertical enamel wrinkles that are more highly developed on the lingual surface of the crown, and decrease in width and number toward the apex. Some of the most promising research related to fossil dentition, involves the analysis of surface and internal dental microstructure. This study, is an attempt to examine and describe polycotylid dental microstructure. It gives an overview of polycotylid plesiosaur enamel and dentine microstructures using a scanning electron microscope. Enamel type and structures vary, based on its position on the surface of the crown, and its perceived strength requirements. The dentition layer is “honeycombed” with tubular structure, possibly to provide nourishment to fast growing crowns. The study of crown microstructures may lead to a better understanding of polycotylid niche preference in the late Cretaceous oceans.