Tooth morphology and prey preference of Mesozoic marine reptiles

Abstract

The large reptilian marine predators of the Mesozoic preyed upon pelagic animals such as bony fish, sharks, soft cephalopods, belemnoids, ammonoids, and even each other. All had undifferentiated conical teeth of one of several forms ranging from a blunt, bulbous shape to a slender, sharply pointed cone, to a robust, slightly compressed cone with two distinct cutting edges. Tooth form, along with tooth wear and occasionally preserved stomach contents, suggests the preferred prey of each species. Seven somewhat overlapping predator types, or guilds, can be defined on the basis of tooth form and prey preference. Members of each guild have tooth morphologies which fall within a defined range, and thus they probably shared the same preferred prey. The guilds present in six well-preserved faunas of the Jurassic and Cretaceous illustrate the structure of and changes in the large marine predator adaptive zone. Six guilds co-existed for most of the Jurassic. Although the composition of some of the guilds changed in the Middle Jurassic, the kinds and number of guilds remained constant. Sometime before the Late Cretaceous, however, there was a major reorganization of the large marine predator adaptive zone resulting in a reduction in the number of reptilian guilds to three. Although the number of guilds increased in the later part of the Late Cretaceous, reptilian predators never attained their earlier diversity before the Cretaceous-Tertiary extinction ended their reign as the dominant large marine predators.