Body form and paleoecology of the large Late Cretaceous bony fish, Pachyrhizodus caninus

Pachyrhizodus caninus Cope is an extinct bony fish found in various Upper Cretaceous marine deposits in North America, but very little has been known about its paleobiology. This paper describes a nearly complete skeleton of P. caninus from the Britton Formation (Cenomanian – lower Turonian) of the Eagle Ford Shale in Texas, USA. The fish specimen is large, measuring 233 cm in total length, and is significant not only because it suggests that P. caninus had a stout tuna-like body with a marlin-like dorsal fin but also because it preserves a partial skeleton of an ichthyodectiform fish representing putative stomach content. This study indicates that P. caninus was a large, active carnivore that swam in open-ocean pelagic environment, much like the comparable-sized, extant tunas and marlins.