Dental topography of prosimian premolars predicts diet: A comparison in premolar and molar dietary classification accuracies

Objectives

This study tests whether (1) premolar topography of extant “prosimians” (strepsirrhines and tarsiers) successfully predicts diet and (2) whether the combination of molar and premolar topography yields higher classification accuracy than using either tooth position in isolation.

Materials and Methods

Dental topographic metrics (ariaDNE, relief index, and orientation patch count rotated) were calculated for 118 individual matched-pairs of mandibular fourth premolars (P₄) and second molars (M₂). The sample represents 7 families and 22 genera. Tooth variables were analyzed in isolation (P₄ only; M₂ only), together (P₄ and M₂), and combined (PC1 scores of bivariate principal component analyses of P₄ and M₂ for each metric). Discriminant function analyses were conducted with and without a measure of size (two-dimensional surface area).

Results

When using topography only, “prosimian” P₄ shape predicts diet with a success rate that is slightly higher than that of M₂ shape. When absolute size is included, premolars and molars perform comparably well. Including both premolar and molar topography (separately or combined) improves classification accuracy for every analysis beyond considering either in isolation. Classification accuracy is highest when premolar and molar topography and size are included.

Discussion

Our findings indicate that molar teeth incompletely summarize the functional requirements of oral food breakdown for a given diet, and that the mechanism selecting for premolar form is more varied than what is expressed by molar teeth. Finally, our findings suggest that fossil P₄s (in isolation or with the M₂) can be used for meaningful dietary reconstruction of extinct primates.