The multiple origins of fossoriality in lizards: morphological evolution of the skull in head-first burrowers

Abstract

Fossoriality has evolved multiple times within lizards, being frequently associated to body elongation and limb loss. Snakelike morphologies have been roughly interpreted as being equivalent, and explanations for the prevalence of limbless elongated phenotypes rescue energetic and biomechanical benefits for burrowing. Most fossorial lizards are head-first burrowers, and modifications in head shape have also been described. Associations between fossoriality and head shape evolution were identified in Gymnophthalmidae, although the two distinct fossorial lineages in this family likely experienced evolutionary processes in the morphological skull diversification process that may have occurred during the colonization of subterranean environments. The current BEPE proposal aims to implement a six-month internship under supervision of Dr. Anthony Herrel at the Muséum National d'Histoire Naturalle of Paris to develop two complementary approaches. Firstly, and in accordance to the main Master study that focuses on morphological evolution of the skull in fossorial gymnophthalmid lizards, we aim to test the resistance imposed by distinct substrates on different skull morphologies during head-first burrowing, using 3D-printed models of gymnophthalmid skulls. Secondly, in order to refine the traditional interpretation of fossorial snakelike morphologies in a broader taxonomic context, we propose an extensive study that uses linear morphometrics to describe head shape evolution among several squamate clades that independently evolved the fossorial habit. (AU)