Abstract

The Amphibamidae are undergoing intensive investigation at present, with many new species recently described to better understand their interrelationships and role in the origin of extant amphibians. A new genus and species of amphibamid, Rubeostratilia texensis, represented by a skull from the Early Permian of Texas, shows many similarities with a recent described species from Richards Spur, Oklahoma, Pasawioops mayi. The skull is elongate and oval, with enlarged external naris and orbits, typical of the other amphibamids within the Micropholis-Tersomius cluster. The skull exhibits the laterally exposed palatine (LEP) and the dorsal quadrate process typical of the Dissorophoidea. Unlike Pasawioops, the new species preserves only a few additional characters relevant to amphibamid relationships: the pterygoid contacts only the ectopterygoid, the postfrontal's shape is falciform, and the alary processes do not extend further posteriorly than one-half of the length of the external naris. We included Rubeostratilia in a recently published amphibamid matrix, to which we added four characters, and conducted two separate phylogenetic analyses, differing in the coding of three characters in the genus Plemmyradytes. The results demonstrate the importance of precision in coding for each character, because these minor changes lead to two different topologies. A brief morphometric analysis of amphibamid cranial anatomy was conducted to better understand the nature of the different morphotypes among which the new species clusters. The results of both morphometric and phylogenetic analysis add support to the emerging consensus that amphibamids cluster into two distinct clades.