Interspecies difference in placement of developing teeth and its relationship with cross-sectional geometry of the mandibular symphysis in four primate species including modern humans
Article first published online: 25 NOV 2011
Copyright © 2011 Wiley Periodicals, Inc.
American Journal of Physical Anthropology
Volume 147, Issue 2, pages 217–226, February 2012
How to Cite
Fukase, H. (2012), Interspecies difference in placement of developing teeth and its relationship with cross-sectional geometry of the mandibular symphysis in four primate species including modern humans. Am. J. Phys. Anthropol., 147: 217–226. doi: 10.1002/ajpa.21640
- Issue published online: 12 JAN 2012
- Article first published online: 25 NOV 2011
- Manuscript Accepted: 12 OCT 2011
- Manuscript Received: 3 MAR 2011
- Japan Society for the Promotion of Science. Grant Number: 22870025
- Cooperation Research Program of Primate Research Institute, Kyoto University
- computed tomography;
- transverse torus
The form of the anthropoid mandibular symphysis has recently been addressed in association with spatial requirements for the forming anterior teeth. To evaluate potential relationships between the symphyseal shape and teeth further, the growth patterns of the symphyseal region and the positioning of the tooth crypts were examined using CT data, comparing four primate species (modern humans, chimpanzees, Japanese monkeys, and hamadryas baboons) with varied symphyseal curvature and tooth size. First, results showed that interspecies differences in overall mandibular shape including symphyseal inclination and bicanine width are consistently expressed throughout postnatal ontogeny, although local symphyseal configurations related to the superior transverse torus (STT) tended to change considerably during growth in chimpanzees. Second, the four species were found to exhibit differentiated formation positions of the incisor and canine crypts. In particular, I2 developed between I1 and C in humans with a broad bicanine space and small teeth, whereas it was positioned posterior to I1 and above C in the cercopithecines with an extremely narrow bicanine space. In chimpanzees, despite the large bicanine width, I1 and I2 grew with a large antero-posterior overlap owing to their large size. These results indicate that the dental positioning is determined in concert with the size balance of the available mandibular space and forming teeth. Finally, the positions/contours of I2 crypt were shown to correspond strongly with the STT across the taxa. This suggests that interspecies differences in symphyseal shape should be interpreted partially by the species-specific positional relationships of the developing anterior teeth. Am J Phys Anthropol 147:217–226, 2012. © 2011 Wiley Periodicals, Inc.