1Department of Anthropology, University of Florida, 2Department of Anthropology, The Ohio State University
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Advances in our understanding of how forces are transmitted through the temporomandibular joint supports the tenet that the size, shape, and material properties of the mandibular condyle are functionally linked to ingestive and masticatory loading environments. This linkage was explored by examining elements of both internal and external mandibular condylar morphology in four sympatric species from the Taï Forest Cȏte d’Ivoire known to differ in diet and feeding behavior: Colobus polykomos (n=6), Procolobus badius (n=6), Cercocebus atys (n=6), and Cercopithecus diana (n=4). Cercocebus atys exploits hard objects and insects, C. diana is primarily frugivorous, and the colobine species are more folivorous, with C. polykomos presumably exploiting a greater quantity of tougher foods than P. badius. We explored variation in condylar trabecular density using mean grayscale values from six areas of each condyle on posteroanterior digital radiographs. Condylar and mandibular dimensions were also recorded.
The species do not differ significantly in mean grayscale values. Most grayscale variance is accounted for by individual variation (49%) or location within the condyle (31%). In all taxa, the lowest grayscale values (i.e., least dense trabeculae) were observed on the lateral aspect of the condyle, an unexpected result considering that the lateral side is thought to be more heavily loaded than the medial side. While the species do not differ in anteroposterior thickness, both colobine taxa exhibit significantly greater mediolateral width compared to the cercopithecines. We propose that this variation in condylar width might reflect masticatory mechanics associated with tougher diets in the former taxa.
Supported by NSFBCS-0922429 and 0921770