Kaiser Thomas M, Fortelius Mikael
Zoological Institute and Museum, University Greifswald, D-17489 Greifswald, Germany.
J Morphol. 2003 Oct;258(1):67-83. doi: 10.1002/jmor.10125.
A new approach of reconstructing ungulate diet, the mesowear method, was recently introduced by Fortelius and Solounias ([2000] Am Mus Novitat 3301:1-36). Mesowear is based on facet development on the occlusal surfaces of the teeth. Restricting mesowear investigation to maxillary cheek teeth would allow mesowear investigation only in assemblages of large numbers of individuals and therefore would generally restrict this method to relatively few assemblages of recent and fossil ungulates. Most of the fossil, subfossil, and recent ungulate osteological assemblages that may be assigned to a single taxon have smaller numbers of individuals. This results in a demand to extend the mesowear method to further tooth positions in order to obtain stable dietary classifications of fossil taxa. The focus of this article is to test if a consistent mesowear classification is obtainable for mandibular as well as for maxillary teeth. For statistical testing, large assemblages of isolated cheek teeth of the Vallesian hipparionine horse Hippotherium primigenium and of the recent zebra Equus burchelli were employed as models. The upper tooth positions P4, M1, M2, and M3 as suggested by Kaiser and Solounias (2003) as the model for the "extended" mesowear method and the lower tooth positions P4-M3 were tested for their consistency in classification of the mesowear variables. We found a considerable shift of the mesowear signature towards the grazing edge of the mesowear continuum in lower cheek teeth. In order to adjust the signal of lower teeth to the signal of the upper teeth, a calibration factor was introduced which allowed incorporation of lower cheek teeth into the same model of mesowear investigation together with upper cheek teeth. We propose that this model is particularly suited for the reconstruction of paleodiets in hypsodont hipparionine and equine equids. We further investigated the functional relation between the mesowear profiles and the distribution of dental tissues along the course of the occlusal contact. We therefore correlated mesowear profiles with enamel distribution profiles and found the mesowear profile to be strongly controlled by the attritional environment encountered by a given apex area. The differential signal observed in cusp apex morphology between upper and lower cheek teeth was found to be more closely related to attrition by the antagonistic tooth than to the distribution of dental tissues in the tooth under consideration. The results suggest a general extension of the mesowear method of paleodiet reconstruction and a basic scenario for the evolution of anisodont dentitions.
一种重建有蹄类动物饮食的新方法——中磨损方法，最近由福泰柳斯和索洛尼亚斯提出（[2000]《美国自然历史博物馆新论》3301:1 - 36）。中磨损基于牙齿咬合面上小平面的发育情况。将中磨损研究局限于上颌颊齿，这意味着中磨损研究只能在大量个体的组合中进行，因此通常会将这种方法限制在相对较少的现生和化石有蹄类动物组合上。大多数可能归为单一分类单元的化石、亚化石和现生有蹄类动物骨骼组合中的个体数量较少。这就需要将中磨损方法扩展到更多的牙齿位置，以便对化石分类单元的饮食进行稳定分类。本文的重点是测试下颌牙齿和上颌牙齿是否能获得一致的中磨损分类。为了进行统计测试，大量孤立的瓦勒斯期始祖马 Hippotherium primigenium 的颊齿和现生细纹斑马 Equus burchelli 的颊齿组合被用作模型。对凯泽和索洛尼亚斯（2003）提出的作为“扩展”中磨损方法模型的上颌牙齿位置 P4、M1、M2 和 M3 以及下颌牙齿位置 P4 - M3 的中磨损变量分类一致性进行了测试。我们发现下颌颊齿的中磨损特征在中磨损连续统中明显向食草边缘偏移。为了使下颌牙齿的信号与上颌牙齿的信号相匹配，引入了一个校准因子，从而可以将下颌颊齿与上颌颊齿纳入同一个中磨损研究模型。我们认为这个模型特别适合于重建高冠始祖马类和马科马属动物的古饮食。我们还进一步研究了中磨损轮廓与沿咬合接触过程中牙体组织分布之间的功能关系。因此，我们将中磨损轮廓与釉质分布轮廓进行了关联，发现中磨损轮廓受到给定尖顶区域所经历的磨耗环境的强烈控制。上下颌颊齿尖顶形态中观察到的差异信号，被发现与相对牙的磨耗关系更为密切，而不是与所考虑牙齿的牙体组织分布密切相关。这些结果表明了古饮食重建中磨损方法的普遍扩展以及异形齿列进化的基本情况。
