Collaborative Research: Integrated Study of an Exceptional Avifauna from the Eocene Green River Formation: New Data on Avian Evolution and Taphonomy

所有现存鸟类出现的模式和时间仍然是脊椎动物系统学中最具争议的问题之一。鸟类化石越来越多地被用作分子分化定年的校准点，并用于检验宏观进化假说。本项目将对北美洲保存最完好的早古近纪鸟类组合进行研究，以快速推进我们对新生代鸟类进化和分类的认识。该组合包括丰富的化石样本，这些化石在不到2000年的时间里沉积在一个湖泊的不同的、已绘制的、具有沉积学特征的亚环境中，保存得非常完好，但在很大程度上没有特征。这些矿床可追溯到50.2+-1.9亿年前，位于怀俄明州的化石丘成员。该项目是第一个将系统分析和对影响主要湖泊组合化石证据的保存偏见的调查结合起来的项目。研究结果有助于：1)从全局角度研究早古近纪鸟类生物多样性；2)了解鸟类辐射的时间和古生物地理格局；3)回答鸟类及其羽毛是如何在关键的湖泊环境中保存下来的基本问题。这些结果将具有更广泛的意义，为在类似环境中保存的其他鸟类化石组合提供比较和指示可能存在偏差的基础，例如早白垩世的热河群中发现了有羽毛的恐龙。发现这些沉积物中可能系统性地缺失了哪些分类群的唯一方法是通过本文提出的方法：在最佳条件下对鸟类多样性最完整的“快照”之一进行系统发育和分类学研究。该项目的广泛影响包括：以标本为基础的解剖学教学、系统的方法和分类学方法的新整合；博士后、博士、本科生培养；通过博物馆展览、相关宣传材料和讲座，促进公众对进化和生物多样性的理解。

The pattern and timing of the emergence of all living birds remain some of the most contentious questions in vertebrate systematics. Avian fossils are increasingly sought as calibration points for molecular divergence dating and used to test macroevolutionary hypotheses. This project will investigate the best-preserved early Paleogene avian assemblage from North America to forward rapidly our understanding of Cenozoic avian evolution and taphonomy. The assemblage comprises a rich sample of exceptionally preserved, but largely uncharacterized, fossils deposited in less than ~2000 years in distinct, mapped, and sedimentologically characterized sub-environments of a single lake. The deposits are tightly dated to 50.2+-1.9 Mya and occur in the Fossil Butte Member in Wyoming. The project is the first to integrate systematic analyses and an investigation of preservational biases that impact fossil evidence from key lake assemblages. The results are essential to gaining: 1) a global perspective on early Paleogene avian biodiversity; 2) an understanding of the timing and paleobiogeographic patterns of the avian radiation; and 3) answers to fundamental questions of how birds and their feathers are preserved in key lacustrine environments. The results will have wider significance in providing a basis for comparison and indication of likely biases in other assemblages of fossil birds preserved in similar settings such as the Early Cretaceous Jehol Group that yields feathered dinosaurs. The only way to discover what categories of taxa may be systematically missing in such deposits is through the approach proposed here: phylogenetic and taphonomic study of one of the most complete 'snap shots' of avian diversity under the best conditions possible. The broader impacts of the project include novel integration of specimen-based teaching of anatomy, systematic methodologies, and taphonomic approaches; postdoctoral, doctoral and undergraduate training; and the promotion of public understanding of evolution and biodiversity via museum exhibits, linked outreach materials, and lectures.