Skinner Matthew M, Gunz Philipp, Wood Bernard A, Boesch Christophe, Hublin Jean-Jacques
Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany.
Am J Phys Anthropol. 2009 Oct;140(2):234-43. doi: 10.1002/ajpa.21057.
Previous research has demonstrated that species and subspecies of extant chimpanzees and bonobos can be distinguished on the basis of the shape of their molar crowns. Thus, there is potential for fossil taxa, particularly fossil hominins, to be distinguished at similar taxonomic levels using molar crown morphology. Unfortunately, due to occlusal attrition, the original crown morphology is often absent in fossil teeth, and this has limited the amount of shape information used to discriminate hominin molars. The enamel-dentine junction (EDJ) of molar teeth preserves considerable shape information, particularly in regard to the original shape of the crown, and remains present through the early stages of attrition. In this study, we investigate whether the shape of the EDJ of lower first and second molars can distinguish species and subspecies of extant Pan. Micro-computed tomography was employed to non-destructively image the EDJ, and geometric morphometric analytical methods were used to compare EDJ shape among samples of Pan paniscus (N = 17), Pan troglodytes troglodytes (N = 13), and Pan troglodytes verus (N = 18). Discriminant analysis indicates that EDJ morphology distinguishes among extant Pan species and subspecies with a high degree of reliability. The morphological differences in EDJ shape among the taxa are subtle and relate to the relative height and position of the dentine horns, the height of the dentine crown, and the shape of the crown base, but their existence supports the inclusion of EDJ shape (particularly those aspects of shape in the vertical dimension) in the systematic analysis of fossil hominin lower molars.
以往的研究表明,现存黑猩猩和倭黑猩猩的物种及亚种可以根据其磨牙冠的形状来区分。因此,利用磨牙冠形态在类似的分类水平上区分化石类群,特别是化石人科动物,是有可能的。不幸的是,由于咬合磨损,化石牙齿中往往不存在原始的冠形态,这限制了用于区分人科动物磨牙的形状信息的数量。磨牙的釉质-牙本质交界处(EDJ)保留了大量的形状信息,特别是关于冠的原始形状,并且在磨损的早期阶段仍然存在。在本研究中,我们调查了下颌第一和第二磨牙的EDJ形状是否能够区分现存倭黑猩猩属的物种和亚种。采用微计算机断层扫描对EDJ进行无损成像,并使用几何形态计量分析方法比较了倭黑猩猩(N = 17)、普通黑猩猩指名亚种(N = 13)和普通黑猩猩西非亚种(N = 18)样本之间的EDJ形状。判别分析表明,EDJ形态能够高度可靠地区分现存倭黑猩猩属的物种和亚种。各分类群之间EDJ形状的形态差异很细微,与牙本质角的相对高度和位置、牙本质冠的高度以及冠基部的形状有关,但其存在支持在化石人科动物下颌磨牙的系统分析中纳入EDJ形状(特别是垂直维度上的形状方面)。