Foraging substrate
We hypothesized that snakes feeding on the ground benefit from the support of a solid substrate to capture, manipulate, and swallow their prey, while arboreal species must deal with gravity and the weight of their body and prey. Aquatic snakes, on the other hand, need to deal with prey buoyancy. Our results indicate a significant difference in tooth shape between terrestrial and aquatic feeders, but not in tooth length. Aquatic snakes have an elbow-like tooth (Fig. 4 Homalopsis buccata , Fig. 5: Laticauda colubrina, Subsessor bocourti ), that is highly medially curved, with a very thin and sharp tip that may be advantageous to prevent prey escape (Fig. 3 & 5). Their pulp cavity runs almost to the tip of the tooth, so the layer of hard tissue is smaller in those teeth which may provide them with more flexibility than terrestrial species. Terrestrial species usually coil around their prey, thus restricting their movement but aquatic snakes usually do not restrain their prey. This may impose forces on the teeth coming from all directions. Thus, having more flexible teeth may be advantageous for aquatic species. This hypothesis remains to be tested but the teeth of aquatically feeding snakes are weakly ankylosed (Savitzky, 1983), suggesting another adaptation to prevent failure of these slender and sharp teeth (Patchell & Shine, 1986).