Robert L. Carroll

Academic paper

Philosophical Transactions of the Royal Society of London, Series B: Biological Sciences

293

315-383

Numerus well preserved fossils from the Upper Permian of Madagascar are structurally intermediate between primitive diapsid reptiles and nothosaurs and plesiosaurs. Claudiamurur germaini (gen.nov., SPJWVA) is similar in its basic anatomy to eosuchian reptiles such as Thadmraurux wlmmzpi (gen.nov., sp.nov.), but the absence of a lower temporal bar and the closure of the palate are characteristics of sauropterygian reptiles. Claudiamurus shows the in iation of aquatic adaptations in the proportions and reduced ossification of the carpus and manusl A third pair of sacral ribs is partially incorporated. The small size of the skull, the nature of the palate and marginal dentition and the long neck are suggestive of aquatic feeding habits. Claudimum does not, however, show the specific adaptations for aquatic locomotion seen in either nothosaurs or plesiosaursl Even the most primitive known species of nothosaurs and plesiosaurs are too specialized in the postcranial skeleton for direct comparison with Claudioxaurux, although the similarities to the skull roof of primitive nothosaurs are very close. Thc configuration of the chcck in nothosaurs almost certainly resulted from the loss of the lower temporal bar from a pattern like that of Ymmgina, rather than from the ventral emargination of the check. The nature of the Upper Permian sediments in Madagascar and the tectonic environment of their deposition indicate accumulation in deep rift valleys, some parts ofwhich were open to the sea, The presence ofoolites replaced with collophane suggests a rich phosphate source such as deep marine upwellings. Similar upwellings of phosphate have also been associated with the evolution of the marine iguanas on the Pacific coast of South America. The concept of the derivation of nothosaurs from protorosaurs or araeosceloids may be traced to misunderstandings of the nature of thc cheek in both Nalhamumx and Praloraxaurux. Araeoxcelix, dcspite the possession of a solid cheek, is closely related to Petralawxaurux, an ancestral diapsid.

English