MAHLER, L.*; KEARNEY, M.; Washington Univ., St. Louis; Field Museum of Natural History; Field Museum of Natural History: The Palatal Dentition in Squamate Reptiles: Morphology, Development, Attachment, and Replacement

The palatal dentition in squamate reptiles is poorly known compared to the marginal dentition. We surveyed species of all squamate families for the presence of palatal teeth. For those exhibiting palatal teeth, we investigated palatal tooth morphology, arrangement, development, attachment, and replacement patterns. We found substantial variability at familial, generic, and specific levels among non-ophidian lizards for the presence of palatal teeth, and for the arrangement and number of palatal tooth rows. However, snakes are much more uniform in both respects. Palatal teeth are morphologically similar to the marginal teeth or, in some cases, relatively simpler. In squamates with palatal teeth arranged in single rows, new teeth develop in the dental lamina along the labial edge of the tooth row. In others, various modifications of the dental lamina accommodate tooth replacement across multiple tooth rows or fields. Ankylosis of palatal teeth occurs either within a shallow resorbed cavity or on a raised ridge on the surface of the element. Tooth replacement patterns on the palate generally mirror those on the dentigerous marginal elements. Patterns of variability found in this study imply tradeoffs between phylogenetic, functional, and developmental constraints. The strong correspondence in morphology and replacement patterns between marginal and palatal dentitions supports the hypothesis of developmental homology between them. In addition, there is some evidence for modularity of palatal tooth expression, and for phylogenetic non-independence of palatal teeth occurring on different palatal bones.