1Department of Anthropology, University of Florida, 2Department of Anthropology, The Ohio State University
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The connections between primate mandibular morphology and dietary variation have been well-studied, but the nature of these relationships remains uncertain. Metric analysis of gross mandibular form has yielded important insights, but the internal structure of mandibular bone is not often considered. Examination of internal features, such as trabecular density and cortical bone thickness, could provide further insight since these variables may reflect modeling and remodeling activity in different loading environments.
Variation in internal mandibular condylar structure was explored using bilateral AP digital radiographs of Procolobus badius (n=6) and Colobus polykomos (n=5) from Taï Forest, Côte d’Ivoire. These sympatric colobines are similar in body size and display moderate sexual dimorphism but appear to differ in dietary habits, with C. polykomos presumably exploiting tougher foods. As a measure of trabecular density, mean grayscale values were taken from six areas of each condyle. In addition, the cortical thickness on the medial and lateral aspects of the condylar neck was measured.
Overall, Procolobus badius and Colobus polykomos do not differ significantly in mean grayscale values or cortical thickness. Most of the variance in grayscale is accounted for by individual variation (41%) or sex (23%). Males tend to have higher grayscale values (i.e., denser trabecular bone) throughout the condyle, on the medial side in particular. Similarly, males exhibit significantly greater cortical thickness on the condylar neck compared to females. Whether these sex differences reflect variation in feeding ecology between males and females is currently being investigated in Taï Forest.
Supported by National Science Foundation grants:BCS-0922429 and 0921770