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As herbivorous, diphyodont mammals with relatively low-crowned molars, primates experience changes in dental function during their lifetimes as teeth become progressively worn. Maintaining tooth function with wear is thought to pose a particular challenge for folivorous primates whose diets emphasize molar shearing actions. Recent studies using dental topographic methods suggest that certain primate folivores have molar morphology that maintains or increases functional shearing surfaces with tooth wear (‘dental sculpting’). Evidence for this phenomenon has been found in folivorous but not frugivorous New World monkeys, supporting the hypothesis that dental sculpting is an adaptive trait linked to diet. This analysis extends these methods to two sympatric Old World monkeys from Sabah, Malaysia, possessing distinct diets and dental morphologies: the folivorous colobine Trachypithecus cristatus (n=25) and the more frugivorous cercopithecine Macaca fascicularis (n=22). For each species, 3D shear crest lengths and four dental topographic variables (relief index, slope, angularity, and Dirichlet Normal Energy [DNE]) were measured from variably worn lower second molars. Preliminary results indicate that for any given degree of wear, Trachypithecus has longer shear crest lengths and higher relief, slope, angularity, and DNE than Macaca. The two species exhibit different patterns and degrees of change in topography and shearing crest lengths across the wear series. However, these changes do not always match expectations based on their respective diets. Correlations between 3D shear crest lengths and other dental topographic measurements suggests that the type of metric used to assess shearing potential may affect whether or not dental sculpting is detected.
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This content will become publicly available on March 12, 2026
Quantifying occlusal wear in extant and fossil primates: A novel approach using the virtual goniometer for wear and dietary analysis
Advancements in 3D scanning and modeling have transformed dental and dietary analyses, yet studies often focus on whole-crown, unworn teeth, limiting sample sizes and scope due to the challenges of analyzing worn teeth. Here we explore a novel quantitative method using a virtual goniometer to measure occlusal wear angles in over 150 worn mandibular second molars from extant primates, including frugivores, folivores, and hard-object consumers. For the first time, we apply this method to fossil primates: Ekembo, Dendropithecus, and Limnopithecus. Using the Hecate software package, we align and subdivide molars into five patches corre- sponding to the cusps. We segment each patch using the virtual goniometer. This segments the occlusal surface from the corresponding buccal, lingual, mesial, and distal surfaces, providing a normal vector corresponding to the plane of best fit for each segment. We then calculate three key angles that describe the plane orientation. Results suggest the inclination measurement from the virtual goniometer is more robust than the average inclination of points in the occlusal surface. Additionally, we find that, among the fossil sample, wear across cusps does not align with any of the tested extant dietary categories. Paleontology is a versatile field of study, applying methods used across disciplines. Our novel approach provides yet another example in which paleontology makes use of versatile computer application by extending the virtual goniometer’s utility beyond archaeological inquiries to primate dental analysis. Additionally, this application offers valuable insight into evolutionary traits associated with dietary behaviors through the inclusion of extant and fossil primates.
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- Award ID(s):
- 2235734
- PAR ID:
- 10584828
- Editor(s):
- Turner, T
- Publisher / Repository:
- American Journal of Biological Anthropology
- Date Published:
- Volume:
- 186
- ISSN:
- 2692-7691
- Page Range / eLocation ID:
- 94
- Format(s):
- Medium: X
- Location:
- Baltimore, MD
- Sponsoring Org:
- National Science Foundation
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