Doctoral Dissertation Improvement: Craniodental Form, Functional Convergence, and the Evolution of Dietary Preferences

长期以来，研究人员一直试图了解早期灵长类动物行为和解剖进化背后的环境变量。尽管对于哪些因素最重要存在分歧，但人们普遍认为饮食起了重要作用。因此，阐明早期灵长类动物进化趋势的努力将需要从化石中重建饮食的能力。为此，在过去的二十年里，研究人员试图确定头骨和牙列的特征，可以用来实现这一目标。虽然这些研究已经确定了许多这样的特征，但仍然存在重大差距。首先，为了确保结构和功能以一种特定的方式始终联系在一起，它们必须在生态相似但又有远亲关系的群体中进行评估。由于很少有预测在非灵长类动物身上得到验证，因此尚不清楚在这些动物身上观察到的模式是否可以自信地推断出它们遥远的化石亲戚。其次，仅仅研究颌骨或牙齿的形状不足以区分所有的饮食。由于以前的研究分别考虑了这两个方面，因此评估这两个方面以充分表征一个物种的摄食习惯的有用性在很大程度上仍未得到探索。这项研究的目的是通过使用有袋动物作为自然实验来测试牙齿和下颌形状反映物种饮食的假设来填补这些空白。具体地说，将评估有关牙齿表面特征和下颌内外比例（由x射线胶片确定）与物种饮食的物理特性的十个预测。通过在一组在喂养生态学的大多数方面与灵长类动物广泛重叠的群体中测试这些预测，这项研究不仅可以更有信心地利用这些变量来推断灭绝灵长类动物的饮食，而且还将极大地扩展我们对哺乳动物进化的生态基础的理解。

Researchers have long sought to understand the environmental variables underlying behavioral and anatomical evolution in early primates. While disagreement persists over which factors were of greatest significance, diet is widely thought to have played an important role. Therefore, efforts to illuminate trends in early primate evolution will require the ability to reconstruct diet from fossils. To this end, investigators over the past two decades have attempted to identify features of the skull and dentition that can be used to achieve this. While these studies have identified many such features, significant gaps remain. First, to ensure that a structure and function are consistently linked in a specified manner, they must be evaluated in ecologically similar, yet distantly related groups. As few predictions have been tested in nonprimates, it is unclear whether patterns observed in these animals can confidently be extrapolated to their distant fossil relatives. Second, the study of jaw or dental form alone is not sufficient to discriminate among all diets. Since previous studies have considered these separately, the usefulness of evaluating both to fully characterize a species feeding habits remains largely unexplored. The goal of this research is to fill these gaps by using marsupials as a natural experiment to test the hypotheses that dental and mandibular form reflect a species' diet. Specifically, ten predictions relating tooth surface features and the internal and external proportions of the lower jaw (determined from x-ray film) to the physical properties of a species' diet will be evaluated. By testing these predictions in a group that extensively overlaps primates in most aspects of feeding ecology, this study will not only allow greater confidence in the utility of these variables for inferring diet in extinct primates, but it will also greatly expand our understanding of the ecological bases of evolution in mammals in general.