Dental Morphologies in Gartersnakes (Thamnophis) and Their Connection to Dietary Preferences

We examined morphological variation in tooth structure in four populations of garter snakes (genus Thamnophis) with diverse feeding habits and tested the hypothesis that morphological homoplasy evolved in the malacophagous predators Thamnophis ordinoides and Thamnophis elegans terrestris. Although long, slender teeth are typical in Neotropical colubrid snake species that prey on slugs and snails, this morphological feature did not occur in T. ordinoides and T. e. terrestris relative to closely related garter snakes (the diet generalist Thamnophis elegans elegans and piscivore Thamnophis couchii). However, we did find pronounced posterior ridges located on the posterior maxillary teeth in the two slug predators but not in the generalist feeders. The evolutionary origin and functional advantage of these ridges has yet to be identified. The fish specialist T. couchii has many morphological features characteristic of adaptations for piscivory, such as long, sharper teeth and elongated mandible bones.