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Mesosaurus is an extinct genus of reptile from the Early Permian of southern Africa and South America. It is a member of the family Mesosauridae and the order Mesosauria. Mesosaurus was long thought to have been one of the first marine reptiles.
Appearance[]
Mesosaurus had a long skull that was larger than that of Stereosternum, with longer teeth. The teeth are angled outwards, especially those at the tips of the jaws. The bones of the postcranial skeleton are thick, having undergone pachyostosis. Mesosaurus is unusual among reptiles in that it possesses a cleithrum. A cleithrum is a type of dermal bone that overlies the scapula, and is usually found in more primitive bony fish and tetrapods. The head of the interclavicle of Mesosaurus is triangular, unlike those of other early reptiles, which are diamond-shaped.