The Late Cretaceous Shark, Ptychodus rugosus, (Ptychodontidae) in the Western Interior Sea

Abstract

Specimens from the Smoky Hill Chalk Member of the Niobrara Chalk in western Kansas previously identified as the Late Cretaceous shark Ptychodus anonymus Williston 1900 are re-diagnosed as P. rugosus Dixon 1850 based on comparisons with the type specimen and other associated tooth sets from the English Chalk. Within the Western Interior Seaway, P. rugosus occurs in Late Coniacian deposits in Kansas and from Santonian deposits in Alabama and Texas. Specimens from the Smoky Hill Chalk are represented by relatively complete tooth sets from individuals of varying ontogenetic stages.