Kley, N. J., E. J. Hilton and A. M. Richmond
The presence or absence of pelvic vestiges has been used as a key character in the study of snake systematics for over a century. However, the anatomy of the pelvic apparatus remains poorly known for most families of snakes, and the variability that exists in pelvic morphology within Serpentes has never been studied within a phylogenetic context. We studied the anatomy of the pelvis and hindlimbs in a phylogenetically diverse sample of scolecophidian and basal alethinophidian taxa in an attempt to elucidate the evolution of pelvic morphology in snakes, and also to identify characters that may be informative in future phylogenetic analyses of Squamata. Although we found high levels of ontogenetic and intraspecific variation in the structure of the pelvis and femur, we also identified several morphological characters which vary interspecifically, and which therefore may be useful for systematic studies. Most significantly, we found several synapomorphies that characterize the pelvic apparatus of basal macrostomatans, including elongate, anterodorsally directed pubes, and highly reduced, cartilaginous ischia and ilia. The reorientation and elongation of the pubes in Macrostomata likely evolved in association with an increased role of the vestigial hindlimb during courtship and mating in this clade.
Ecology & Evolutionary Biology - Brown University