Functional morphology of the skull in Lysorophus : a snake-like Paleozoic amphibian (Lepospondyli)

Lysorophus , a serpentiform, nearly limbless, aquatic Paleozoic amphibian was described in detail by Sollas in 1920. Although Sollas did not discuss cranial kinesis, his original reconstructions suggest that Lysorophus had an unusually kinetic skull for an amphibian. We have reexamined the skull of Lysorophus and find that kinesis, if present, was slight. The maxillae, premaxillae, and vomers might have moved in limited protraction and retraction, with the premaxillae rotating about their contacts with the nasals. There is a possibility of small medio-lateral movements of the lacrimal and maxilla as a unit at the lacrimal-prefrontal joint. The skull of Lysorophus shows many features convergent with the skulls of burrowing reptiles, such as amphisbaenians. Modifications in the skull of Lysorophus from a more primitive tetrapod condition seem associated with burrowng in a soft substratum rather than with kinesis per se.