Meeting Abstract
The genus Varanus encompasses a diverse and speciose group of reptiles, which occupy a broad range of ecological niches, and are endemic to three continents (Africa, Asia, and Australia). Phylogenetic analyses show a number of independently derived semi-aquatic lineages, with closely related terrestrial and/or arboreal species, exhibiting a strong relationship between body shape and ecology. The goal of this project is to compare tail skeletal morphology between terrestrial and semi-aquatic species, and identify any convergent trends. Varanids are an especially appropriate model system for studying the transition from terrestrial to marine environments due to their hypothesized close relationship to mosasaurs; however, this relationship has recently been called into question. Previous work focusing on vertebrae from the neck to the pelvic girdle has demonstrated measurable differences in in zygapophyses, articular surfaces, and centrum lengths, all of which are likely related to forces generated during swimming. Reptiles that swim via undulation increase their propulsive surface by having dorsoventrally expanded, laterally compressed tails. The difference in muscle force needed for swimming versus non swimming locomotion, as well as the change in overall tail shape, may also be reflected in the morphology of the caudal vertebrae. Using CT data, we have reconstructed tail vertebrae from 15 species of varanids and from Green Iguana and Marine Iguana specimens, and have measured and compared neural spine, transverse process, and centrum morphology.
