STRATIGRAPHIC EVIDENCE FOR THE EXTINCTION OF THE ICHTHYOSAURS

The extinction of ichthyosaurs is not well understood both in terms of time and of causation although it is supposed to have happened at some point of the Late Cretaceous. Four species of ichthyosaurs attributed to the single cosmopolitan genus Platypterygius Huene, 1922 are currently recognized from the Albian and Cenomanian, but after that time only fragmentary remains have been described. A review of these available post-Cenomanian ichthyosaur remains reveals that all are doubtful either from a stratigraphic or a systematic point of view. Ichthyosaur extinction may be tentatively correlated with the Cenomanian-Turonian boundary events. During this interval, biological factors such as a break in the food chain attested by severe extinction in marine invertebrates, especially belemnites, may have led to the extinction of ichthyosaurs.