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Anatomy Research International
Volume 2011 (2011), Article ID 929848, 11 pages
Research Article

The Jaw Adductor Resultant and Estimated Bite Force in Primates

1Department of Anatomy, Midwestern University, 555 31st Street, Downers Grove, IL 60515, USA
2Departments of Biology and Anthropology, Penn State University, 3000 Ivyside Park, Altoona, PA 16601, USA

Received 16 December 2010; Revised 1 March 2011; Accepted 9 May 2011

Academic Editor: Adam D. Sylvester

Copyright © 2011 Jonathan M. G. Perry et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We reconstructed the jaw adductor resultant in 34 primate species using new data on muscle physiological cross-sectional area (PCSA) and data on skull landmarks. Based on predictions by Greaves, the resultant should (1) cross the jaw at 30% of its length, (2) lie directly posterior to the last molar, and (3) incline more anteriorly in primates that need not resist large anteriorly-directed forces. We found that the resultant lies significantly posterior to its predicted location, is significantly posterior to the last molar, and is significantly more anteriorly inclined in folivores than in frugivores. Perhaps primates emphasize avoiding temporomandibular joint distraction and/or wide gapes at the expense of bite force. Our exploration of trends in the data revealed that estimated bite force varies with body mass (but not diet) and is significantly greater in strepsirrhines than in anthropoids. This might be related to greater contribution from the balancing-side jaw adductors in anthropoids.