Doctoral Dissertation Improvement: Paleoecological Modeling and the Evolution of Early Eocene Primates in the Bighorn Basin, WY

本研究旨在进一步加深对最早灵长类动物起源和进化的认识。一个广泛的、多学科的方法将被用来分析已知的最完整的早期灵长类化石序列之一。虽然对古生物学和古生态学（研究古代生态系统的相互作用）也会做出重要贡献，但这个项目的主要目标是将灵长类动物的进化与环境和群落变化联系起来。怀俄明大角盆地的威尔伍德地层包含了早期现代哺乳动物历史的非凡记录。它沉积于5500万至5250万年前，是世界上最丰富、最连续的始新世早期序列之一。灵长类动物是威尔伍德组保存的动物群中重要而多样的组成部分，在许多威尔伍德组合中占10-20%的个体。来自比格霍恩盆地南部的大部分化石地点被捆绑在一个近700米厚的复合沉积剖面中，该剖面暴露在3000多平方公里的面积上。自20世纪60年代初以来，大量的化石收集工作一直集中在大角盆地南部，导致了大量的化石收集，保守估计包括多达10万种脊椎动物标本。近年来，大角盆地的古环境研究引入了稳定同位素分析的创新，以表征这些沉积物的气候和沉积环境。这些新数据与以往基于化石土壤和植物叶片地貌的古环境重建结果非常吻合。随着这些令人兴奋和多样化的证据线的出现，现在有可能在严格限制的时间框架和不断变化的区域环境的背景下研究威尔伍德灵长类动物的进化。这类研究在“古生态学”的标题下松散地分组，在形成灵长类动物和原始人进化的假设方面至关重要。本项目拟分两个阶段对大角盆地南部哺乳动物群落进行古生态分析。第一个是量化，使用随机抽样程序，在始新世的前250万年，在大角盆地南部的动物进化模式。初步分析表明，曾经发生过集中的动物群变化（更替）。在第二阶段，将对结果模式进行测试，以确定其是否与目前关于进化变化的八种不同生态模型假设的预测相符。这项研究的结果将对最早灵长类动物的进化情景和围绕古代生态系统古生态模型的当前争论具有重要意义。这项研究的广泛影响将包括对当前围绕气候变化对现代哺乳动物生态系统影响的辩论的贡献。这些结果将说明面对区域温度和湿度的变化以及地质环境的变化，古代生态系统的行为和进化。此外，更广泛的影响包括Co-PI的研究生培训。收集的数据将对进一步的研究有用，并将推动Co-PI的科学事业。

This study is proposed to advance the current understanding of the origin and evolution of the earliest primates. A broad-based, multidisciplinary approach will be used to analyze one of the most complete sequences of early fossil primates known. Though important contributions will also be made to the sciences of paleontology and paleoecology (the study of the interactions of ancient ecosystems), the main goal of this project is to relate primate evolution to environmental and community changes. The Willwood Formation of the Bighorn Basin, Wyoming, contains an extraordinary record of the history of early modern mammals. Deposited between 55 and 52.5 million years ago, it is one of the richest and most continuous early Eocene sequences in the world. Primates formed a significant and diverse element of the fauna preserved in the Willwood Formation, accounting for 10-20% of the individuals from many Willwood assemblages. Most of the fossil localities from the southern part of the Bighorn Basin have been tied into a composite sedimentary section of nearly 700m in thickness that is exposed over an area of more than 3000 km2.Intense fossil collecting efforts have been focused in the southern Bighorn Basin since the early 1960s, resulting in an enormous collection of fossils conservatively estimated to include as many as 100,000 vertebrate specimens. Recently, paleoenvironmental studies of the Bighorn Basin have incorporated innovations in stable isotope analysis to characterize the climate and depositional environment of these sediments. These new data are in excellent accord with previous paleoenvironmental reconstructions based on fossil soils and plant leaf physiognomy. With the emergence of these exciting and varied lines of evidence, it is now possible to examine the evolution of the Willwood primates in a tightly constrained time frame and in the context of a changing, regional environment.Studies of this type, grouped loosely under the heading 'paleoecology', have been critical in shaping hypotheses of primate and hominid evolution. The proposed project aims to accomplish a paleoecological analysis of the southern Bighorn Basin mammal community in two stages. The first is to quantify, using a random-sampling procedure, the pattern of faunal evolution during the first 2.5 million years of the Eocene in the southern Bighorn Basin. Preliminary analysis suggests that there have been episodes of concentrated faunal change (turnover). In the second stage, the resultant pattern will be tested for correspondence with the predictions of eight different current hypotheses of ecological models for evolutionary change. The results of this study will have important implications for scenarios of the evolution of the earliest primates and current arguments surrounding the paleoecological modeling of ancient ecosystems.The broader impacts of this study will include a contribution to current debates surrounding the impact of climate change on modern mammalian ecosystems. The results will illustrate the behavior and evolution of an ancient ecosystem in the face of changing regional temperature and moisture regimes, and shifting geological environments. In addition, the broader impacts include the graduate training of the Co-PI. The data collected will be useful in further research and will advance the scientific career of the Co-PI.