Mosasaur ascending: The phylogeny of bends

Abstract

Recognition of decompression syndrome-related pathology (in the form of avascular necrosis) reveals diving behaviour in mosasaurs. Macroscopic and radiologic examination was performed to identify linear bone death characteristic of avascular necrosis in vertebrae from the major North American and European collections. This survey of mosasaurs extends throughout most of their geographic and stratigraphic range and includes examples across their diversity. Avascular necrosis was invariably pres ent in Platecarpus coryphaeus and P. ictericus, Tylosaurus proriger, Mosasaurus lemonnieri and M. conodon, Plioplatecarpus houzeaui and Pl. primaevus, Prognathodon giganteus, Hainosaurus bernardi and an as yet unnamed Antarctic mosasaur. The frequency of occurrence in a given genus was independent of geography, present equally in European and North American and in the Niobara and Selma chalks. It was invariably absent from Clidastes propython and C. liodontus, Ectenosaurus, Halisaurus and Kolposaurus. The bone pathology, avascular necrosis, has a characteristic distribution in seven genera and thirteen species of mosasaurs and is absent in five genera and seven species. It segregated according to diving habits, uniformly present in supposed deep divers and uniformly absent in the shallow-habitat group.