ANATOMY OF THE SKULL AND BRAINCASE OF A NEW DEINOSUCHUS RUGOSUS SPECIMEN FROM THE BLUFFTOWN FORMATION, RUSSELL COUNTY, ALABAMA

A well-preserved posterior skull of Deinosuchus rugosus, with an intact braincase, was discovered in the Upper Cretaceous (Campanian) Blufftown Formation in Russell County, Alabama. This new specimen enabled descriptive analysis of the braincase of this primitive alligatoroid and revealed favorable comparisons of cranioquadrate passages to the same region of Alligator mississippiensis. However, a modern A. mississippiensis shows more elongate supratemporal fenestrae and a gentler incline of the prefrontal ridge than D. rugosus. Due to the smaller size of this Deinosuchus skull compared with other eastern specimens, we conclude the individual was a juvenile.

An enigmatic Upper Cretaceous fossil from the Black Creek Formation of North Carolina, putatively a very large Deinosuchus braincase, was also compared with this new Alabama specimen. Similarities between the specimens are in the placement of the sutures, ridges, and foramina. From a posterior-ventral aspect, the fossil represents the left exoccipital and quadrate of Deinosuchus. The cranium of Deinosuchus rugosus has not been previously available for detailed study because of generally poor specimens, and the new information enhances the position of Deinosuchus in the basal phylogeny of Alligatoroidea.