BITE ME - BITE MARKS ON A MOSASAUR SKULL FROM THE SMOKY HILL MEMBER OF THE CRETACEOUS NIOBRARA FORMATION, KANSAS

Previously studied mosasaur specimens from the late Cretaceous Western Interior Seaway have exhibited tooth marks, gouges and other evidence of injuries. These marks have proven to be from other mosasaurs and various shark species that suggest predation behavior or territorial defense mechanisms.

This study focuses on a juvenile or young adult Tylosaurus kansasensis specimen recovered from the Smoky Hill Chalk Member of the Niobrara Formation in northwestern Kansas. The specimen exhibits a variety of markings and damage to the right side of the skull, as well as a mosasaur tooth, embedded cusp downward, in the posterior right dentary. Bone density scans, CT scans, and microscopic examination were used to determine the origin of the extraneous tooth; more specifically whether the tooth belonged to this animal or another mosasaur, how the tooth became embedded in the dentary, and what its presence indicates about the probable cause of death.

The results of the examinations indicate forceful emplacement of the tooth, suggesting that only another, larger mosasaur could have inflicted a bite with sufficient force to result in such extensive damage. Less severe, minor grooving and gouging may have been the result of subsequent scavenging by sharks, post mortem. Evidence also suggests the emplaced tooth may be the specimen's own pterygoid tooth, forced into the dentary when the skull was crushed by the larger mosasaur.