Permo-Triassic "lizards" from the Karroo

Carroll, Robert L
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Bernard Price Institute for Palaeontological Research
Three genera of sauropsid reptiles from the Permo-Triassic beds of South Africa - Saurosternon Huxley, Paliguana Broom and Palaegama Broom - were originally described as lizards, or the immediate ancestors of that group. Restudy of these forms confirms that they are close to the ancestry of later Mesozoic and Cenozoic squamates. The skull is somewhat primitive, but in size, proportions and function extremely similar to that of Kuehneosaurus. The pectoral girdle is lacertoid in the proportions and orientation of the clavicles and interclavicle; the anterior margin of the scapulocoracoid is fenestrate, and the articulating surface of the glenoid is very short. A sternum is present and one specimen shows ventral connections between the ribs and the sternum. In Saurosternon, the forelimb can be seen as very similar to that of living lizards, with special epiphyseal articulating surfaces on the proximal end of the humerus and distal end of the ulna. The pelvic girdle remains primitive, but the rear limb is close to the pattern in lizards. The fifth metatarsal is not obviously hooked, and all five distal tarsals are retained, but the proportions and functions of the ankle presage the condition in living lizards. Epidermal scales are present. Following Romer, these forms are all included in the Family Paliguanidae. They are placed in the Suborder Lacertilia, provisionally in the Infraorder Eolacertilia.
Diapsid , Beaufort Group