First Associated Tooth Set of Ptychodus anonymus (Elasmobranchii: Ptychodontidae) in North America from the Jetmore Chalk in Kansas

Abstract

Isolated tooth specimens of the Late Cretaceous shark Ptychodus anonymus Williston 1900 are common occurrences in the Cenomanian and Turonian deposits throughout the Western Interior Seaway. Reported here is an association of 58 teeth of P. anonymus (FHSM VP-19170) recovered from the Jetmore Member of the Greenhorn Formation (Late Cenomanian) in Mitchell County, Kansas. This specimen is significant as it represents the first occurrence of an associated dentition of this species. A single vertebra was also collected, which makes this the stratigraphically oldest occurrence of Ptychodus with associated post cranial remains. This tooth set consists of teeth from seven tooth file positions to the right and left side of a central medial file. This specimen demonstrates the complete heterodonty pattern in the dentition of P. anonymus, clarifying the morphological variations that exist in isolated teeth ascribed to the species. This specimen provides additional clues to determine the ordinal taxonomic classification of the family.