Doctoral Dissertation Improvement: Ecological and Morphological Correlates of Infraorbital Foramen Size: Paleontological Implications

在过去的世纪里，灵长类动物的进化起源引起了人们的极大关注。为了解释灵长类动物与其他哺乳动物在进化上的差异，人们提出了几种相互竞争的假说。 这些假说强调的重要性，如饮食，基板的偏好，和活动模式的变量时，重建灭绝的灵长类动物和他们的前辈的行为和生态概况。 颅骨特征的形态学分析经常被用来检验这些假设。 眶下孔（IOF）是一种已用于此功能的形态学特征。IOF位于上颌骨（面部）的眶下缘下方。 眶下神经（ION）穿过IOF，并将感觉信息从上唇、腭肌和触须的专门触觉细胞（机械感受器）传递到大脑。几十年来，研究人员一直使用IOF的大小来分配化石灵长类动物的进化关系和生态概况。然而，这些解释是基于未经测试的假设，连接IOF大小的ION大小，触须的发展，和生态。 这个博士论文研究项目的目的是建立什么样的IOF大小表明功能和生态，并将结果应用于化石记录，以评估提出的灵长类动物起源的竞争假说。 这位博士生假设，哺乳动物之间的行为和生态差异直接影响面部感觉敏锐度（上颌机械感受性），IOF的大小是哺乳动物面部相对感觉敏锐度的量度。 本研究提出了三个问题，将有助于评估这一假设。1)IOF大小与IOF面积、ION面积和触须数相关吗？2)生态学（例如，饮食）影响IOF大小？3)与其他哺乳动物相比，灵长类动物的IOF大小如何？ IOF/ION面积和触须计数的数据将收集在哺乳动物尸体，骨骼博物馆标本和毛皮，代表18个哺乳动物目的遗传和生态多样性的样本。 一旦IOF面积，上颌mechanoreception和生态之间的关系，确定现存的哺乳动物，结果将被应用到灵长类动物的进化和多样化的问题。 由于化石记录的不完整性，验证这些假设有时很困难。 然而，IOF是一种经常在化石中保存的解剖学特征。因此，这项研究的结果将允许扩展以前的古生态学分析，并将提高我们目前对早期灵长类动物进化的理解。在更广泛的影响方面，这个项目将有助于培养一名研究生。 由于在这项研究中解决的问题将探讨使用不同的哺乳动物样本，确定的IOF大小的相关性将适用于古人类学和一般哺乳动物古生物学研究的进化问题。

The evolutionary origin of primates has attracted considerable attention over the past century. Several competing hypotheses have been proposed to account for the evolutionary divergence of primates from other mammals. These hypotheses emphasize the importance of variables such as diet, substrate preference, and activity pattern when reconstructing the behavioral and ecological profiles of extinct primates and their predecessors. Morphological analyses of cranial features are frequently employed to test these hypotheses. The infraorbital foramen (IOF) is one morphological feature that has been used in this capacity. The IOF is located below the inferior orbital margin of the maxilla (face). The infraorbital nerve (ION) passes through the IOF, and transmits sensory information from specialized touch cells (mechanoreceptors) of the upper lip, rhinarium, and vibrissae to the brain. For decades, researchers have used the size of the IOF to assign evolutionary relationships and ecological profiles to fossil primates. However, these interpretations are based on untested assumptions linking IOF size to ION size, vibrissal development, and ecology. The purposes of this doctoral dissertation research project are to establish what IOF size indicates functionally and ecologically and to apply the results to the fossil record in order to evaluate competing hypotheses proposed for the origin of primates. The doctoral student hypothesizes that behavioral and ecological differences among mammals directly affect facial sensory acuity (maxillary mechanoreceptivity) and that the size of the IOF is a measure of relative sensory acuity of the face among mammals. This study poses three questions that will assist in appraising this hypothesis. 1) Does IOF size correlate with IOF area, ION area, and vibrissa number? 2) How does ecology (e.g., diet) affect IOF size? 3) How does IOF size in primates compare to that of other mammals? Data on IOF/ION area and vibrissa counts will be collected on a phylogenetically and ecologically diverse sample of mammalian cadavers, osteological museum specimens and skin pelts, representing 18 mammalian orders. Once the relationships among IOF area, maxillary mechanoreception, and ecology are determined among extant mammals, the results will be applied to questions regarding the evolution and diversification of primates. Testing these hypotheses is difficult at times, given the fragmentary nature of the fossil record. However, the IOF is one anatomical feature that is frequently preserved in fossilized remains. Therefore, the results of this study will allow for an expansion of previous paleoecological analyses and will enhance our current understanding of the evolution of early primates.In terms of broader impacts, this project will help train a graduate student. Because the questions addressed in this study will be explored using a diverse mammalian sample, the determined correlates of IOF size will be applicable to evolutionary questions in both paleoanthropological and general mammalian paleontological research.