Meeting Abstract
A snake-like body plan and burrowing lifestyle characterize countless vertebrate groups through convergent evolution. One such group is the amphisbaenians, a limbless clade of lizards that are primarily fossorial and exhibit head-first burrowing behavior. Correlated with this behavior, amphisbaenian skulls are recognized as more rigid and coossified than those of non-burrowing lizards. However, due to their elusive lifestyle, amphisbaenian skulls are not yet well understood, including how cranial osteology may vary among individuals of the same species and what that reveals about constraints on skull morphology of head-first burrowing taxa. We investigated intraspecific variation in the cranial osteology of amphisbaenians using Diplometopon zarudnyi. Variation among skull and skull element morphology was analyzed qualitatively and by performing 3D landmark-based geometric morphometrics on 3D models created from microCT data. Significant differences were observed in the length of dorsal contact between the parietal and occipital complex, the interdigitation of the frontals and parietal, and the degree of coossification between the occipital complex, fused basioccipital and parabasisphenoid, and Elements X. These results reveal significant variation in suture interdigitation and morphology of the occipital region in D. zarudnyi, indicating that the variation may be the result of different stages of ontogenetic development or that these regions may have less strict morphological constraints in head-first burrowing taxa. Examination of this variation across other head-first burrowing taxa will help determine if this is clade-specific or part of a broader macroevolutionary pattern.
