Acroplous vorax Hotton (Amphibia, Saurerpetontidae) restudied in light of new material. American Museum novitates ; no. 2662

Supplemental Materials
Journal Title
Journal ISSN
Volume Title
New York, N.Y. : American Museum of Natural History
"A new individual of Acroplous vorax is described and its systematic position within the Saurerpetonidae is reexamined. The new specimen is clearly conspecific with the type as shown by the narrow midline elements, broad supratemporal and intertemporal, wide but short lacrimal, and nearly identical pterygoids. The new specimen offers more data on the braincase, pterygoid occiput, lower jaw, and humerus. The internal process of the pterygoid is small and a well-developed epipterygoid caps the dorsal process of the pterygoid, indicating a more primitive basal articulation than that interpreted for Isodectes. Unfortunately, the condition in Saurerpeton is unknown for comparison. Like all other saurerpetonid genera (Dvinosuarus, Saurerpeton, Isodectes) the lower jaw has a large symphysial tusk and a long retroarticular process. The new material, however, is primitive in having a small posterior meckelian fossa. Advanced lower jaw characters are an overall dorsoventral compression and a unique wide exposure of the articular both laterally and medially. The vertebrae are unique among saurerpetontids in having a cartilaginous portion of pleurocentrum conspicuously larger than the intercentrum. A hypothesis of relationships suggests Acroplous to be the sister group of Isodectes and brachyopids. As a result the saurerpetontids are paraphyletic since they exclude the brachyopids. Further, if brachyopids are the sister group to 'saurerpetontids' and other stereospondyls are more closely related to eryopids, then stereospondyls would be diphyletic. There are many characters, however, that contradict the hypothesis of stereospondyls being diphyletic. Dvinosaurus, long thought to be an aberrant member of the trimerorhachoids, is thought to be the sister group to 'saurerpetontids' and brachyopids"--P. [1].
27 p. : ill. ; 26 cm.
Includes bibliographical references (p. 26-27).