Daegling D J
Department of Anthropology, University of Florida, Gainesville, Florida 32611-7305, USA.
J Morphol. 2001 Oct;250(1):12-23. doi: 10.1002/jmor.1055.
Experimental investigation of mandibular bone strain in cercopithecine primates has established that the mandible is bent in the transverse plane during the power stroke of mastication. Additional comparative work also supports the assumption that the morphology of the mandibular symphysis is functionally linked to the biomechanics of lateral transverse bending, or "wishboning" of the mandibular corpus. There are currently no experimental data to verify that lateral transverse bending constitutes an important loading regime among hominoid primates. There are, however, allometric models from cercopithecoid primates that allow prediction of scaling patterns in hominoid mandibular dimensions that would be consistent with a mechanical environment that includes wishboning as a significant component. This study uses computed tomography (CT) scans to visualize cortical bone distribution in the anterior corpus of a sample of four genera of extant hominoids. From the cortical bone contours, area properties of the mandibular symphysis are calculated, and these variables are subjected to an allometric analysis to detect whether scaling of jaw dimensions are consistent with a wishboning loading regime. Scaling of the hominoid symphysis recalls patterns observed in cercopithecoid monkeys, which lends indirect support for the hypothesis that wishboning is an integral part of the masticatory loading environment in living apes. Inclination of the symphysis, rather than changes in cross-sectional shape or development of the superior transverse torus, represents a morphological solution for minimizing the potentially harmful effects of wishboning in the jaws of these primates.
对猕猴亚目灵长类动物下颌骨应变的实验研究已证实，在咀嚼的动力冲程中，下颌骨在横向平面内发生弯曲。额外的比较研究也支持这样一种假设，即下颌联合的形态在功能上与下颌体的横向弯曲或“叉骨状”生物力学相关联。目前尚无实验数据来验证横向弯曲是否构成类人猿灵长类动物的一种重要负荷状态。然而，来自猕猴科灵长类动物的异速生长模型可以预测类人猿下颌尺寸的缩放模式，这些模式将与一个包括叉骨状作为重要组成部分的力学环境相一致。本研究使用计算机断层扫描（CT）来可视化现存四类类人猿样本下颌体前部的皮质骨分布。根据皮质骨轮廓计算下颌联合的面积属性，并对这些变量进行异速生长分析，以检测颌骨尺寸的缩放是否与叉骨状负荷状态一致。类人猿联合部的缩放让人想起在猕猴科猴子中观察到的模式，这间接支持了叉骨状是现存猿类咀嚼负荷环境不可或缺的一部分这一假设。联合部的倾斜度，而非横截面形状的变化或上横嵴的发育，代表了一种形态学解决方案，可将叉骨状在这些灵长类动物颌骨中产生的潜在有害影响降至最低。
