Publication Date
10-9-1987
Series Number
201
Abstract
Limnoscelis paludis historically has been considered close to the ancestry of reptiles. Although the unique holotype skeleton is largely complete, its braincase has never been adequately described. Recent mechanical preparation has exposed the braincase laterally, dorsally, and in cross section for the first time, and has enhanced the preexisting ventral and occipital views, Newly revealed attributes include a fused basiparasphenoid, a fused otic, a feebly ossified zone separating anterior and posterior braincase divisions, paired basiparasphenoid ossifications of the dorsum sellae, a sphenethmoid with Y-shaped transverse cross section, an ossified synotic, a concave occipital condyle, reduced exoccipitals, and the absence of posttemporal fenestrae. Cladistic analysis of many cranial characters, including those of the braincase, indicates that among Paleozoic tetrapods, Limnoscelis is most closely related to the diadectomorphs Tseajaia and Diadectes. The diadectomorphs are primitive reptiles, most closely related to the pelycosaurs.