Meeting Abstract
Chameleons are well known for numerous highly characteristic anatomical and behavioral features such as their projectile tongue, prehensile tail, independently rotating eyes, and color changing abilities. With over 200 described taxa in twelve genera, however, chameleons are extremely diverse in their own right and come in a great variety of unique shapes and sizes. Among the most variable skeletal features in chameleons is the number of presacral (cervical, thoracic and lumbar) and caudal vertebrae, as well as the number of sternal and parasternal ribs. In fact, chameleons are known to have 14-23 presacral vertebrae, 17-62 caudal vertebrae, 3-4 sternal ribs, and 5-11 parasternal ribs. This variation, however, is based on the examination of a limited number of taxa and has not been put into a proper phylogenetic or ecological context (e.g., more arboreal vs. terrestrial species). We gathered and examined micro computed tomography (micro-CT) scans from 233 chameleon specimens, representing 155 different species of chameleon and five additional subspecies. This sample represents seventy-five percent of all described chameleon species, including all genera, and a previously unmatched body of data on the structure and function of this lizard family. From this examination, we quantified the rib and vertebral numbers across the family, including variation within genera. We then tested whether this variation correlates most closely with ecological characteristics or phylogenetic relationships within the family. These results provide insight into the evolution and function of the axial skeleton in chameleons and the morphological evolution of the axial skeleton across disparate ecological environments.
