Previous studies report that geometric measures of incisor size and curvature in extant anthropoid primates correspond to dietary differences. However, other methodologies of assessing incisor shape variation, such as dental topographic analysis, have not been considered.
This study measures Relief Index (RFI), linear dimensions, and curvature of central mandibular incisors (I) for a sample of extant anthropoids (n = 107). The utility of these measures in enhancing dietary separations across Anthropoidea is further investigated using traditional and phylogenetic statistics, principal component analysis, and multinomial logistic regression.
Two-way ANOVAs find significant dietary differences and no sexual differences in I height, width, breadth, and RFI across crown anthropoids. Phylogenetic ANOVAs also detect significant dietary differences in these measures despite the presence of high and significant phylogenetic signal in height and RFI, indicating that dietary signals are robust. Predictive models combining I geometry and RFI outperform those using solely I geometry. A mixed-feeding ecology is inferred for the fossil platyrrhine Antillothrix.
Our findings indicate that I RFI and linear dimensions are robust dietary proxies in anthropoid primates that may be beneficial to future ecomorphological and paleontological analyses. The presence of phylogenetic signal merits further investigation, and we recommend a nuanced approach if applying I RFI or height as a dietary proxy for fossil primates.

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