What can be seen of the lower jaw indicates that it was primarily formed by the dentary in its front half, and the low, elongated surangular and angular in its rear half. The coronoid had a low peak and the tall articular had a small retroarticular process. Only one tooth was exposed, and it was similar to those of the maxilla, albeit smaller. The articulated postcranial skeleton is weathered to the point that only portions of the cervical vertebrae and interclavicle are in good enough condition to describe. The cervicals had slight excavations on their outer surface, robust neural arches, and low neural spines, with that of the axis overhanging its predecessor. The interclavicle is anchor-shaped (like ankyramorph, or "anchor-form" parareptiles), but in contrast to ankyramorphs, the center of the interclavicle is thicker than the front edge. Overall the postcranium is congruent with that known for Milleretta. Classification The original describers of Australothyris used a phylogenetic analysis designed by Muller & Tsuji (2007) to investigate its relations to other parareptiles. The analysis found that it had an optimal position as a relatively basal parareptile, specifically the sister taxon to Ankyramorpha (the group containing lanthanosuchoids and more derived parareptiles). This was nevertheless more derived than mesosaurs and millerettids, and the paper's authors assigned the name Procolophonomorpha to parareptiles more derived than millerettids. Australothyris was recovered as the first branch of Procolophonomorpha, suggesting that the group as a whole originated simultaneously with the evolution of a large, fully enclosed temporal fenestra in parareptiles. However, the subsequent discovery of Microleter, which had a roughly equivalent phylogenetic position and a much more restricted temporal emargination, casts doubts on this hypothesis for the origin of temporal fenestration. Certain millerettids have also been observed to possess temporal fenestrae. The position of Australothyris also supports another hypothesis which argues that procolophonomorphs evolved in Gondwana (southern Pangea) before spreading to and diversifying in more northern regions, although Microleter, known from Oklahoma, once more casts doubt on this hypothesis. Cladogram after Modesto, Scott, & Reisz (2009). References Procolophonomorphs Permian reptiles of Africa Fossil taxa described in 2009 Prehistoric reptile genera