Molar Cervical Root Cross-Sectional Morphology and Diet in Extant Catarrhines

External tooth root morphology has demonstrated utility in understanding the mechanical function of teeth including patterns of loading during mastication and the overall mechanical challenge of foods consumed. Yet, there is still a paucity of information regarding how signals of diet, apart from these patterns, might be reflected in root form. This study examines whether a cross-section taken from the molar root cervix contains signals related to diet and masticatory function in extant catarrhine primates.

Micro-CT scans of 11 genera of catarrhines were used to obtain 188 mandibular molars (M₁, M₂, and M₃) from the right side. A single slice taken from the cervical margin was used to generate cross-sectional properties for analysis.

OLS regression of dentin area on mandibular length provided evidence of a strong relationship (r² = 0.90-0.93, p < 0.001) and analysis of the residuals indicated significant differences for dietary category. Post hoc tests revealed that soft and hard object frugivores differ in relative dentin area across the molar row (p < 0.05). Additionally, a ratio calculated from the second moments of area I_x and I_y describing the cross-sectional dentin distribution showed that dentin allocation was also significantly associated with dietary category serving to distinguish hard object frugivores from all other groups.

The cervical root cross-section contains information regarding both the mechanical function of a tooth as well as conveying some aspects of dietary specialization, particularly for frugivorous catarrhines. This region provides a more nuanced understanding of dental adaptation along the folivore-frugivore continuum.