Collaborative Research: SG: Early evolution of the modern North American freshwater fish fauna: New Late Cretaceous sturgeons, paddlefishes, bowfins, and teleosts from North Dakota

从1亿年前到6500万年前的晚白垩世，是北美淡水鱼类发生巨大变化的时期。许多较老的鱼类种群正在灭绝，取而代之的是现代种群。但现代群体从何而来，他们如何以及为什么取代了较老的群体？除了其他问题外，这些问题都没有得到回答，因为这个时期的鱼类化石记录非常糟糕。该项目分析了一个关键时期(7200万-6600万年前)新发现的完整淡水鱼骨骼化石。这些化石保存得非常完好，提供了一个难得的完整骨骼的一瞥。该项目将填补在理解现代淡水鱼起源和进化方面的一个关键空白。除了这个项目的科学价值，还有几个更广泛的影响。首先，将描述的化石保存在可公开获取的自然历史收藏品中，从而确保科学界可以永久使用它们。其次，围绕化石的准备和分析制定的学生培训计划为初出茅庐的科学家提供了有价值的研究和培训。第三，这项研究的结果将以科学文章的形式发表，并在专业会议和研讨会上向公众介绍。最后，通过利用芝加哥菲尔德自然历史博物馆现有的资源，该项目将增加公众对科学的理解。所有标本都将在实验室中准备，每年参观菲尔德博物馆的120多万名参观者，包括许多K-12学生团体和教师，都可以在那里观察到对标本的积极准备和研究，这种保存精美的鱼类化石动物群的临时展览将为菲尔德博物馆目前的展品增加一个重要组成部分。尽管北美的现代淡水鱼动物群已经得到了深入的研究，但其起源、生物地理和进化史仍然知之甚少，部分原因是缺乏来自白垩纪淡水沉积物的全身化石，特别是那些含有关节骨骼的化石。这项研究使用了最近在北达科他州马斯特里赫特地狱溪组中发现的保存异常完好的拉格斯塔滕鱼类化石，来阐明早中生代(由灭绝的目和科组成)和现代淡水动物群之间的过渡。最近发现的含有许多淡水鱼的铰接完整骨骼的块已经被菲尔德博物馆获取用于准备和分析。所有化石都将使用物种解剖的所有方面的详细照片记录相结合的方式进行描述和说明，并配以线条图，清楚地显示形态的解释。这些数据将构成原始形态描述、特征概念化以及对区块中存在的关键鱼类谱系的系统发育和比较分析的基础，包括鲟科、多齿鱼科、鳗科、斑鱼科，可能还有真鱼。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Late Cretaceous, from 100 million to 65 million years ago, was a time of great change for the freshwater fishes of North America. Many older groups of fishes were going extinct and being replaced by modern groups. But where did the modern groups come from, and how and why did they replace the older groups? These questions, among others, are unanswered because the fossil record of fishes from this time period is extremely poor. This project analyzes newly discovered, complete fossilized skeletons of freshwater fish from a critical time period (72-66 million years ago). These fossils are extraordinarily well-preserved, providing a rare glimpse of complete skeletons. This project will fill a critical gap in understanding the origin and evolution of modern freshwater fish. In addition to the scientific merit of this project, there are several broader impacts. First, the fossils to be described are deposited in publicly accessible natural history collections, thereby ensuring that they are available in perpetuity to the scientific community. Second, student training programs developed around the preparation and analysis of the fossils provides valuable research and training for budding scientists. Third, results from this study will be published in scientific articles and presented at professional meetings and seminars for public audiences. And finally, by using the resources available at the Field Museum of Natural History in Chicago, the project will increase public understanding of science. All specimens will be prepared in a lab where active preparation and study of the specimens can be observed by the more than 1.2 million annual visitors to the Field Museum, including many K-12 student groups and teachers, and a temporary exhibit of this exquisitely preserved fossil fish fauna will add an important component to current exhibits at the Field Museum. Although the modern freshwater fish fauna of North America has been intensively studied, its origin, biogeography, and evolutionary history are still poorly understood, due in part to a lack of whole-body fossils from Cretaceous freshwater deposits, particularly those containing articulated skeletons. This study uses exceptionally well-preserved fossil fish from a recently discovered lagerstatten in the Maastrichtian Hell Creek Formation of North Dakota, to illuminate the transition between the early Mesozoic (consisting of extinct orders and families) and the modern freshwater fauna. Recently discovered blocks containing the articulated, complete skeletons of many freshwater fish have been acquired by the Field Museum for preparation and analysis. All fossils will be described and illustrated using a combination of detailed photographic documentation of all aspects of the anatomy of the species with matched line drawings clearly showing the interpretation of the morphology. These data will form the basis of original morphological descriptions, character conceptualization, and phylogenetic and comparative analyses of key fish lineages present in the blocks, including the Acipenseridae, Polyodontidae, Amiidae, Lepisosteidae, and possibly Teleostei.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.