The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Functional Correlates of Cochlear Shape


1Interdepartmental Doctoral Program in Anthropological Sciences, Stony Brook University, 2Department of Anthropology, University of Texas at Austin, 3Department of Anthropology, New York University

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Previous research on the functional morphology of the primate cochlea has demonstrated that hearing abilities are correlated with cochlear volume and basilar membrane length. Here we assess the functional utility of cochlear shape for estimating high frequency limit, low frequency limit, and best frequency of hearing in a sample of 12 primate species. Two cochlear shape indices (CSI) were developed to measure the height of the cochlea relative to its width and were measured from high resolution CT scans of the bony labyrinth. Phylogenetic generalized least squares regressions were calculated in R to determine associations between both shape indices, hearing parameters, and body mass. CSI 1 is positively correlated with best frequency (n = 12; R2 = 0.455; p > 0.05) and CSI 2 is positively correlated with high frequency limit (n = 12; R2 = 0.453; p < 0.05). CSI 1 and CSI 2 are not associated with either low frequency limit or body mass. These results suggest that the gross shape provides another metric for estimating hearing ability in primates in addition to cochlear volume and basilar membrane length. However, preliminary observations also suggest that lorisiforms and lemuriforms differ systematically in cochlear shape, although differences in hearing ability have not been suggested for these two clades. Future analyses will address whether these patterns hold with greater sampling and the utility of cochlear shape as a tool for recognizing phylogenetic groups.

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