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。虽然在哪些因素最重要的问题上仍然存在分歧，但人们普遍认为饮食在其中发挥了重要作用。因此，阐明灵长类早期进化趋势的努力将需要从化石重建饮食的能力。为此，研究人员在过去20年里一直试图确定可以用来实现这一点的头骨和牙列的特征。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，为了确保一种结构和功能以特定的方式一致地联系在一起，它们必须在生态上相似但关系遥远的群体中进行评估。由于很少有预测在非灵长类动物身上进行测试，目前还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的远亲化石。其次，仅对颌骨或牙齿形态的研究不足以区分所有的饮食。由于以前的研究已经分别考虑了这两个因素，因此对两者进行评估以充分描述一个物种的觅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类动物作为自然实验来填补这些空白，以检验牙齿和下颌形态反映物种饮食的假设。具体地说，将评估与牙齿表面特征和下颌骨的内外比例(由X光胶片确定)与物种饮食的物理特性有关的10项预测。通过在摄食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，这项研究不仅将使人们对这些变量在推断已灭绝灵长类动物的饮食方面的效用有更大的信心，而且它还将极大地扩大我们对哺乳动物总体进化的生态学基础的理解。

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.