A Pennsylvanian ‘supershark’ from Texas

ABSTRACT

The occipital regions of the braincases of two gigantic ctenacanthiform sharks are described from the Finis Shale (Virgilian, Upper Pennsylvanian, ca. 300 Ma) of Texas. Their original braincase lengths are estimated to have been 42.8–68.2 and 33.9–64.8 cm, based on comparison with smaller, more complete ctenacanthiform specimens (e.g., Tamiobatis). In complete ctenacanthiform body fossils (e.g., Goodrichthys), braincase length represents approximately 10% of total body length. This suggests that the Finis Shale sharks attained lengths up to 7 m (as large as modern great white sharks and Cretaceous cardabiodontids) and body weights of 1500–2500 kg. As apex predators, such large sharks probably maintained a high hepatosomatic index and may even have utilized lamnid-like heat exchange retia in critical parts of the body (e.g., brain, eyes, stomach).

Citation for this article: Maisey, J. G., A. W. Bronson, R. R. Williams, and M. Mckinzie. 2017. A Pennsylvanian ‘supershark’ from Texas. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1325369.

ACKNOWLEDGMENTS

Financial support for this research was provided by the H. and E. Axelrod Research Chair in Paleoichthyology at the American Museum of Natural History. The Dallas Paleontological Society is recognized and thanked for its encouragement and support of paleontological research in Texas, without which this material might have gone unnoticed. The specimens were photographed in the AMNH by L. Meeker and the late C. Tarka. L. Meeker also drafted the locality map. We thank J.-P. Hodnett for generously providing us with measurements of the new ctenacanth shark specimen in the New Mexico Museum of Natural History and Science.