Dietary adaptation in lemurs, analyzed using new approaches to describing functional properties of tooth shape

The postcanine teeth of mammals are shaped by the requirements of food fracture. Tooth shape descriptors attempt to quantify those aspects of tooth form that reflect adaptation to the fracture of foods differing in material properties. Dental topography metrics, which capture features of whole occlusal surfaces using digital scans, have shown promise in classifying mammals, particularly primates, to dietary ecology. However, they suffer from potential issues arising from digital mesh processing, model overfitting, and the averaging of functional signal among tooth structures that are under potentially independent selection. Here, these issues are addressed using a recently developed dental topography metric (ariaDNE) which is less sensitive to details of mesh processing; Bayesian multinomial modelling with metrics designed to measure overfitting risk; and a tooth segmentation algorithm which allows the shapes of disaggregated tooth surface features to be quantified using dental topography metrics. ariaDNE quantifies tooth curvature using a method comparable to the originally described Dirichlet Normal Energy (DNE), but averages over local bandwidths of a tooth surface in a process that is robust to variation in tooth face count and smoothing algorithms. Combinations of dental topography metrics that included ariaDNE outperformed DNE in reclassifications of individual specimens and genera by their genus means using discriminant function analysis. Bayesian multinomial models suggest that informationally rich models including other metrics may overfit in out‐of‐sample reclassifications, however. Disaggregating teeth into regions of consistent shape did not improve predicted reclassification success, suggesting that averaging of morphological information across the tooth surface does not interfere with the ability of dental topography metrics to predict dietary adaptation. ariaDNE presents a powerful tool for the description of functional shape that can be applied to a wide range of taxa and potentially aspects of morphology across the body. Support or Funding Information Funding was provided by the Duke Graduate School dissertation research domestic travel grant and summer research support and by the grants NSF BCS 1552848 to Doug Boyer, NSF BCS 130405 to Doug Boyer and Elizabeth St. Clair, and NSF BCS 1825129 to Doug Boyer and Arianna Harrington.