Meeting Abstract
Recumbirostra is a group of small tetrapods from the Late Carboniferous and Early Permian generally interpreted as stem-lissamphibians, stem-caecilians, or stem-amniotes. We present an expanded phylogenetic dataset to investigate the phylogenetic relationships of recumbirostrans among early tetrapods, incorporating substantial new braincase data gleaned from broad application of micro-CT to numerous recumbirostran fossils. Phylogenetic analysis of both braincase and postcranial characters supports a placement of this group within crown amniotes, along the reptile stem. These phylogenetic results simplify interpretations of the evolution of the ankle, middle ear, and otoccipital region. Unique recumbirostran characteristics do not strongly support alternate phylogenetic hypotheses, contra previous studies, and are uniformly consistent with stereotypical headfirst burrowing morphology among modern squamates. This suggests that early reptiles rapidly filled specialized niches characteristic of modern squamates in ways that other Paleozoic tetrapods did not.
