Doctoral Dissertation Research: Unraveling primate supraordinal relationships: Insights from plesiadapiform cranial morphology

灵长类动物--人类所属的哺乳动物群体--起源的核心是灵长类动物的化石，这些化石是由灵长类和近亲哺乳动物组成的一个群体(Euarchonta)的已灭绝成员。虽然一些适应灵长类动物长期以来一直被认为与一些当代灵长类动物具有相同的特征，但使用更新的、最先进的方法对适应灵长类动物进行额外的分析可以进一步推进我们对灵长类动物起源的理解。本博士论文利用高分辨率X射线微电子计算机断层扫描(μCT)等方法，分析和比较了脊椎动物与现存灵长类及其他胎盘哺乳动物的颅骨解剖结构。在一个新的进化树的背景下，产生了详细的头骨比较，可以增加对灵长类动物、现存的灵长类动物和其他真主哺乳动物之间进化关系的评估。该项目还通过导师指导、公共科学参与活动和数据共享提供了大量的外联机会。来自该项目的见解可以被纳入促进STEM中代表性不足的群体参与的计划。研究人员还在CT扫描数据处理、3D打印、计算机编码和基本化石准备方面培训本科生和硕士生。研究人员计划将该项目产生的所有数据，如CT扫描数据和数据矩阵，免费提供给公共在线储存库，以允许重复性和未来对灵长类进化的研究。Plesiadiform颅骨传统上在灵长类动物起源的假说中发挥着重要作用，但仍然知之甚少，因为它们对大多数鸭嘴兽物种来说是未知的，因为许多已知的头骨标本没有使用现代CT技术进行分析。这项研究使用现代高分辨率CT技术来记录新的鳍状颅骨解剖结构，重新评估以前发表的颅骨描述，并在灵长类和其他胎盘哺乳动物之间进行彻底的颅骨比较。这些数据被合并到一个新的特征-分类单元矩阵中，该矩阵使用简约和贝叶斯系统发育方法进行分析，以评估进化关系。这些分析的结果可以让研究人员评估(I)如果有的话，哪些头骨特征是现代方面的拟适应类和灵长类唯一共有的，(Ii)类适应类家族之间的相互关系，以及(Iii)真尾目类内类类进化关系的假说。最终，这些新的数据可以澄清先前提出的具有现代特征的灵长类和灵长类动物之间的共同头骨特征，并将促进更好地理解灵长类动物与其他哺乳动物的差异以及灵长类进化历史的第一步。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Central to unraveling the origin of primates - the mammalian group to which humans belong - are the fossils of plesiadapiforms, extinct members of a group (Euarchonta) consisting of primates and closely related mammals. While some plesiadapiforms have long been suggested to share characteristics with some contemporary primates, additional analyses of the plesiadapiforms using newer, state-of-the-art methodologies can further advance our understanding of primate origins. This doctoral dissertation project uses methods such as high-resolution X-ray micro computed tomography (μCT) to analyze and compare the cranial anatomy of plesiadapiforms to that of extant primates and other placental mammals. Detailed cranial comparisons are generated that can add to the evaluation of evolutionary relationships among plesiadapiforms, extant primates, and other euarchontan mammals, in the context of a new evolutionary tree. This project also provides numerous opportunities for outreach through mentorship, public science engagement events, and data sharing. Insights from this project can be incorporated into programs that facilitate participation from groups underrepresented in STEM. The investigators also train undergraduate and master’s students in aspects of CT scan data processing, 3D printing, computer coding, and basic fossil preparation. The investigators plan to make all data generated from this project, such as CT scan data and data matrices, freely available on public online repositories to allow for repeatability and to enable future studies on primate evolution.Plesiadapiform crania have traditionally played an important role in hypotheses about primate origins but remain poorly understood because they are unknown for a large majority of plesiadapiform species and because many of the known cranial specimens have not been analyzed using modern CT techniques. This study uses modern high-resolution CT technology to document new plesiadapiform cranial anatomy, reevaluate previously published cranial descriptions, and make thorough cranial comparisons among primates and other placental mammals. These data are incorporated into a new character-taxon matrix that is analyzed using both parsimony and Bayesian phylogenetic methods to assess evolutionary relationships. Results from these analyses can allow investigators to assess (i) which, if any, cranial features are uniquely shared among plesiadapiforms and primates of modern aspect, (ii) interrelationships among plesiadapiform families, and (iii) hypotheses of plesiadapiform evolutionary relationships within Euarchonta. Ultimately, these new data can provide clarity on previously proposed shared cranial features among plesiadapiforms and primates of modern aspect and will promote a better understanding of the divergence of primates from other mammals and the first steps in primate evolutionary history.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.