Collaborative Research: Effects of Climatic/Environmental Change on Early Eocene Mammal Fauna of the Bighorn Basin, Wyoming

气候/环境变化对怀俄明州大角盆地早始新世哺乳动物区系的影响摘要：为了了解气候/环境变化如何影响动物区系进化，美国国家自然科学研究院将对怀俄明州大角盆地中部早始新世Willwood组哺乳动物区系的变化进行分析。来自中央大角盆地的哺乳动物化石记录是这种分析的理想选择，因为它密度大，研究广泛，连续分布，并与精细的气候/环境背景直接相关。该地区的威尔伍德组的底部包括古新世/始新世极热期（PETM），这是一个短暂而突然的全球变暖事件，与新生代哺乳动物历史上最剧烈的一次更替事件有关。在这个序列中发现的另外两个较小的更替事件似乎与气候变化相对应，但证据是模棱两可的。这个项目和其他正在进行的工作应该有助于澄清这些事件。该研究的目标是收集高分辨率、密集采样的动物变化记录，这些记录跨越古新世/始新世边界，以及早始新世前30年在比格霍恩盆地中部，特别是针对采样不足的区间。这将使从时间间隔相等的连续样本的比较，以评估物种更替模式，丰度，多样性，相对体型，以及在始新世早期营养结构的变化。由此产生的一段时间内动物区系变化的综合记录将用于测试这些动物区系变化与气候/环境变化之间的相关性。特别令人感兴趣的是温度变化的幅度和方向的变化以及降水的波动对动物群的影响。

Collaborative Research: Effects of Climatic/Environmental Change on Early Eocene Mammal Fauna of the Bighorn Basin, WyomingKenneth D. Rose and Amy E. Chew, co-PIsABSTRACT In order to understand how climatic/environmental change influences faunal evolution, the PIs will analyze changes in the mammalian faunas of the early Eocene Willwood Formation in the central part of the Bighorn Basin, Wyoming. The record of fossil mammals from the central Bighorn Basin is ideal for this analysis as it is dense, extensively studied, continuously distributed and directly associated with a fine-scale climatic/environmental context. The Willwood Formation in this area includes at its base the Paleocene/Eocene thermal maximum (PETM), a brief and abrupt episode of global warming, which is associated with one of the most dramatic turnover events in the history of Cenozoic mammals. Two other lesser turnover events recognized in this sequence appear to correspond to climatic shifts, but the evidence is equivocal. This project and other ongoing work should help to clarify these events. The goal of the study is to assemble a high-resolution, densely sampled record of faunal change across the Paleocene/Eocene boundary and during the first 3my of the early Eocene in the central Bighorn Basin, especially targeting under-sampled intervals. This will enable a comparison of successive samples from time-equal intervals, in order to evaluate patterns of species turnover, abundance, diversity, relative body size, and change in trophic structure during the early Eocene. The resulting comprehensive record of faunal change over time will be used to test the correlation between these faunal changes and climatic/environmental changes. Of particular interest will be the effect on faunas of variation in the magnitude and direction of shifting temperature and of fluctuation in precipitation.