A new species of Palaeohypotodus Glückman, 1964 (Chondrichthyes, Lamniformes) from the lower Paleocene (Danian) Porters Creek Formation, Wilcox County, Alabama, USA

Abstract

The historic collection of the Geological Survey of Alabama includes several fossil shark specimens that were recovered from the lower Paleocene Porters Creek Formation in southwestern Alabama, USA. Among these specimens are 17 teeth that we herein recognize as a new species within the extinct Paleogene genus, Palaeohypotodus. Detailed examination of these individual teeth, coupled with analyses of the dentitions of various extant lamniform sharks, allowed us to confirm monognathic and dignathic heterodonty within Palaeohypotodus. We identified upper and lower anterior and lateral tooth files that can be differentiated from one another by minor variations in morphology. Additionally, numerous isolated teeth from other Danian exposures in Alabama and Arkansas, USA, enhance our understanding of the composition of the dentition and ontogenetic heterodonty of both the new species and the genus as a whole.