NANNAROTER MCKINZIEI, A NEW OSTODOLEPID 'MICROSAUR' (TETRAPODA, LEPOSPONDYLI, RECUMBIROSTRA) FROM THE EARLY PERMIAN OF RICHARDS SPUR (FT. SILL), OKLAHOMA

A newly discovered, small lepospondyl from the Early Permian of Oklahoma is demonstrated to be a new genus and species of ostodolepid 'microsaur' and is given the name Nannaroter mckinziei. The holotype and only known specimen comes from the Permian-aged fissure fill deposits in the Ordovician limestone from the Dolese Brothers Limestone Quarry, the richest, most diverse Paleozoic assemblage of exclusively terrestrial vertebrates. The superbly preserved skull is identified as the smallest known ostodolepid for its characteristic cranial architecture. Like all ostodolepids, it has a wedge-shaped skull with a high posterior profile and broad occipital surface, and a lower temporal emargination. Like ostodolepids, gymnarthrids, pantylids, and Rhynchonkos, the anterior rostrum is overturned, producing a recumbent snout. Despite its small size, Nannaroter has a massively ossified skull with deeply interlocking sutures designed to tightly resist anteroposteriorly directed forces. Medial laminae are present on all circumorbital bones producing thick orbital walls, and there is a well-developed ventral process of the frontal that is suturally attached to the sphenethmoid portion of the braincase anterodorsally. In addition, a massive, triangular pterygoid-epipterygoid complex reinforces the posterolateral wall of the braincase and contacts the tabular and parietal portion of the dermatocranium. This description is the first part of a revision of the ostodolepids, which will explore adaptations in amphibians to a fossorial lifestyle.