Meeting Abstract
Placodonts, a group of extinct marine reptiles from the mid to late Triassic, are inferred to have consumed hard prey by crushing their shells, and their teeth are typically described as low, round, or flat. Tooth size and position are variable both across the diversity of placodonts and in an individual. Here we explore how the anatomy of the occlusal surface varies, with focus on the ability of the tooth to break hard prey and resist damage from the gustatory efforts. Flat teeth will break shelled prey with less force than cupped teeth, and with as much or less force than domed teeth. Pointed crowns make tooth failure more likely compared to flat or cupped surfaces. Based on these trade-offs, we predicted an ‘optimal’ shape for crushing teeth: a tooth with a flat or shallowly convex occlusal surface which can both crush shelled prey items while resisting tooth failure. Teeth that vary from the predicted morphology may suggest a different diet or indicate that some other aspect natural history is at play. Shape was quantified by measuring the occlusal radius of curvature from all placodont genera. Differences in radius of curvature between species agrees with the predicted pattern, with conical or rounded teeth, occurring in groups closer to the base of the tree, where hard prey was not as important in the diet. Flatter teeth were found in most of the true hard prey specialists. However, in the placochelyids, a lineage of the late Triassic, the main crushing teeth do not follow this trend, but instead have a more complex morphology suggests an unappreciated dietary specialization or an alternate approach to crushing.
