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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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Examining Dietary Diversity in a Paleogene Hyrax (Afrotheria, Mammalia) Fauna from the Fayum Depression, Egypt using Mesowear Analysis
With most ungulates absent from Africa until the Miocene, the morphologically diverse hyraxes were a major component of the Eocene-Oligocene community at Quarry L-41 (~34 Ma) in the Fayum Depression, Egypt. However, their foraging strategies are poorly understood. This study focuses on four extinct hyraxes: Thyrohyrax meyeri, Thyrohyrax litholagus, and Megalohyrax eocaneus, all expected to be grazers; and Saghatherium bowni, previously described as a browser. Mesowear can place extinct herbivores on a spectrum from grazer to browser based on the abrasiveness oftheir lifetime diets. Crown height, tooth length, and cusp angle were measured for the first lower molars (M1) in these four hyrax species. Specimens were categorized into Wear Classes (WC), which correspond with developmental age. WC ranged from 1, first adult molar fully erupted, to 8, all molars extremely worn with significant dentin exposure. Change in mean crown height and cusp angle across different wear classes was not significantly different. Nonetheless, apparent trends suggest compositional differences in diet. Change in mean crown height for Saghertherium indicates that it incorporated more graze than browse because M1 wear occurred in earlier WCs and increased throughout life. In contrast, less wear for WC 1 through 4 in Thyrohyrax indicates that it incorporated more browse. This agrees with recently collected carbon isotope data, which suggests that Saghatherium’s diet included more graze than Thyrohyrax’s. These data are consistent with the description ofThyrohyrax as an arboreal browser. The change in mean crown height for Megalohyrax also suggests a less abrasive diet, although sample size for Megalohyrax was smaller. The browse-biased diet for Megalohyrax is surprising, as isotope values suggest a more open environment. Browsing in salt-stressed environments, forest canopies or forest edges could explain these combined data. Megalohyrax could have foraged in a wider variety of environments than the other taxa because its larger size enabled a wider range. By reconstructing the diets and niche partitioning among morphologically diverse hyraxes at L-41, we hope to gain insights about the ecosystem represented by L-41 near the Eocene-Oligocene Boundary (EOB). This locality represents a time of ecological dynamism when many mammalian communities were dramatically restructured, though the impact of the EOB on African mammal communities remains poorly understood.
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- Award ID(s):
- 2023087
- PAR ID:
- 10523471
- Publisher / Repository:
- Society of Vertebrate Paleontology
- Date Published:
- Subject(s) / Keyword(s):
- Mammals, Cenozoic, Paleogene, Paleoecology
- Format(s):
- Medium: X
- Location:
- Annual Meeting of the Society of Vertebrate Paleontology in Cincinnati, Ohio
- Sponsoring Org:
- National Science Foundation
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