New Information on the Basal Pelycosaurian-Grade Synapsid Oedaleops

Abstract

The Early Permian amniote Oedaleops is generally considered to be one of the basalmost pelycosaurian-grade synapsids. Thus it occupies a key position for understanding the phylogenetic relationships of basal synapsids specifically and basal amniote interrelationships more generally. This assessment has until now been based almost exclusively on the remains of a single skull from the Lower Permian Cutler Formation of north-central New Mexico. The identification of additional cranial as well as numerous postcranial elements of at least three additional individuals now permits a more complete understanding of its anatomy and allows the first attempt at a partial body reconstruction of this basal pelycosaurian-grade synapsid. Oedaleops is confirmed as an extremely basal synapsid taxon, but the addition of postcranial data from Oedaleops to data matrices of earlier phylogenetic analyses unexpectedly weakens, as opposed to strengthens, support for the hypotheses of a monophyletic Eothyrididae.