An anatomical and systematic study of the family Mesosauridae (Reptilia; Proganosauria) with special reference to its associated fauna and palaeontological environment in the Whitehill Sea

Abstract

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The anatomy and taxonomy of the southern African fossil reptile Mesosaurus from the Whitehill Shale Formation, its palaeo-ecology and associated fauna were studied

A study of the biozonationing of the Whitehill Shale has shown that the Formation is a chronostratigraphic unit. It is postulated that the almost identical Whitehill and Iraty Formations were deposited in shallow contemporaneous embayments of a central sea arm that occupied a position between the two continents. The water body was stratified with anoxic, toxic, bottom brines that prevented the establishment of a benthonic fauna. A study of the newly collected fossil material led to a new interpretation of the cranial morphology of Mesosaurus and it was found to be anapsid and closely allied to Limnoscelis. If M. tenuidens is to be regarded as typical for the Mesosauridae, all the members of the order Proganosauria will have to be transferred to the order Cotylosauria

M. tenuidens was found to differ from M. brasiliensis and is the only species of Mesosaurus in the southern African Permo-Carboniferous Whitehill Formation. Along with it two more forms, Noteosaurus africanus Broom and a yet unidentified species, identical with or closely allied to Stereosternum tumidurn occur