Palaeopathology and injury in the extinct mosasaurs (Lepidosauromorpha, Squamata) and implications for modern reptiles

Three fossilized dentaries provide an insight into the healing of fractures in a major group of extinct marine predators, mosasaurs. The data has implications for modern day reptiles in which such information is scanty. All three dentaries have callus formation. Both dentaries of Mosasaurus hoffmanni show fracture non-union, possibly resulting from intervening tissue. They also show evidence of osteomyelitis. Bone remodeling is complete in an earlier fracture in one of the M. hoffmanni dentaries. Given that the most recent fracture (non-union) occurred at a new and much deeper part of the dentary and not in the region of the earlier fracture, it can be assumed that remodeled bone in mosasaurs (probably in reptiles generally) could withstand powerful stresses such as those encountered during predation and fighting. The splenial bone, attached in life to the dentary only by connective tissue, may have acted as a natural splint to immobilize the fracture to the dentary and maintain its alignment during healing. Possible explanations for the injuries are feeding on hard-shelled prey, such as turtles, and fighting.