A LATE CRETACEOUS DUROPHAGUS SHARK, PTYCHODUS MARTINI WILLISTON, FROM TEXAS

摘要

The Late Cretaceous durophagus shark previously described as Ptychodus connellyi (Family Ptychodontidae) by MacLeod & Slaughter is here diagnosed as a junior synonym of Ptychodus martini Williston. The occurrence of the holotype (SMU-SMP 69031) in the Roxton Limestone Member (upper Lower Campanian) of the Gober Chalk in Fannin County, Texas is significant both geographically and stratigraphically. Whereas the present fossil record suggests that P. martini is endemic to the Western Interior Sea, this specimen represents the only record of P. martini outside Kansas. If the tooth was not subjected to any significant reworking, the specimen not only represents the youngest occurrence for the species, but also one of the youngest occurrences of the genus and family.