The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Does the primate pattern hold up? Testing the functional significance of infraorbital foramen size variation among marsupials


1Department of Anthropology, University at Albany – SUNY, 2Department of Anatomy and Neurobiology, University of Kentucky

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The infraorbital nerve, which passes through the infraorbital foramen (IOF), provides sensory innervations to the upper lip, face and vibrissae. The IOF has been used to interpret the ecology of extinct primates for several decades. In primates, relative IOF area covaries with diet, where frugivores have relatively larger IOFs than folivores or insectivores. Currently, it is unknown if the above described ecological pattern holds outside the primate order. Here, we examine how relative IOF area varies across marsupials occupying different ecological niches. Marsupials were chosen because they converge with primates in both ecology and morphology. IOF area and cranial length were collected from 41 marsupial species to generate a measure of relative IOF area. An ecological profile (diet and substrate preference) was created for each marsupial sampled and each was classified as a faunivore, folivore, fungivore, frugivore, or gramnivore and as either terrestrial or arboreal. Results show relative IOF area did not vary significantly between terrestrial and arboreal species. However, relative IOF area differed significantly by diet category (p = 0.019). Species that specialize in feeding on non-grassy leaves have significantly smaller relative IOF areas than species which primarily feed on grasses, insects, vertebrates, or some combination thereof. Behavioral analyses for a subset of the folivores in this study suggest that this difference is due to a greater reliance on hands for feeding. These results, combined with earlier work in primates, suggest that relatively small IOF area may reflect increased reliance on hands in relation to diet, but not substrate.

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