The cranial morphology of the temnospondyl A ustralerpeton cosgriffi ( T etrapoda: S tereospondyli) from the M iddle– L ate P ermian of P araná B asin and the phylogenetic relationships of R hinesuchidae

Stereospondyls are a diverse and morphologically distinctive clade of basal tetrapods that rapidly reached a global distribution and high abundance during the E arly T riassic. Y et, the first stereospondyls appeared in the M iddle– L ate P ermian of G ondwana, mostly represented by R hinesuchidae. A ustralerpeton cosgriffi is a long‐snouted representative of the group and one of the most complete temnospondyls known from the P ermian of S outh A merica. The elements attributed to Au . cosgriffi were recovered from the Middle‐ L ate P ermian deposits of the R io do R asto F ormation ( P araná B asin), in the S erra do C adeado area of B razil. Here, we review the cranial anatomy of the species, providing a comparative redescription, new anatomical data and previously unrecognized characters. A ustralerpeton cosgriffi is nested within R hinesuchidae based on the anatomy of the tympanic cavity, but its long‐snouted condition is unique amongst rhinesuchids. Based on the recovered information and new morphological data, the systematic position of Au . cosgriffi was assessed using a new matrix of 221 characters; of which 196 were selected from previous studies and the remaining are newly proposed. The results show R hinesuchidae divided into R hinesuchinae and A ustralerpetinae. A unique tympanic cavity formed by a well posteroventrally projected tabular horn, stapedial groove, well‐developed oblique crest on the pterygoid, and a dorsal pterygoid crest (new term) characterizes the ear region of R hinesuchidae. A ustralerpeton cosgriffi is the only undisputed R hinesuchidae record outside southern A frica and the first long‐snouted S tereospondyli, and thus is useful in helping to understand the diversification of the stereospondyls during the M iddle/ L ate P ermian of G ondwana.