Meeting Abstract
Most placodonts, an extinct clade of Triassic marine reptiles, were durophagous and had highly modified crushing teeth, but evolved from an ancestor that did not consume hard-prey. Over time this group evolved a dental battery that could both effectively break hard shells, and persist as a functional unit despite wear. We used laser scan and CT data to examine changes in tooth shape and replacement rate across placodont phylogeny. More basal species have overall convex maxillary and palatal teeth, with many replacement teeth at various stages of development, but show no replacement pattern. The more derived armored placodonts can be separated into two groups: the Cyamodontidae and the Placochelyidae. Maxillary and palatal teeth of the cyamodontids are moderately convex, and the caudal-most palatal teeth are functionally flat. The cyamodontids have reduced the number of replacement teeth, and replace teeth in functional units. All placochelyid teeth have concave occlusal surfaces, and the caudal-most teeth feature a cusp along the medial edge of the concavity. These organisms have one or two replacement teeth at a time, with at least one replacement tooth growing under the most posterior palatine tooth. These changes in tooth morphology and tooth replacement indicate increased specialization for prey crushing in the cyamodontoid radiation relative to more basal species and support the hypothesis that placochelyid species had a different dietary specialization.
