Exploring biodiversity evolution in tropical seas based on comparisons of the Triassic fauna of the Cassian Formation with modern faunas

三叠纪卡西安组产生了异常多样的海洋热带无脊椎动物动物群，为早期中生代生态系统的复杂性和生物多样性提供了基本公正的评估。动物群由来自不同地区和不同古环境的不同组合组成，其多样性和组成差异很大。化石保存通常是例外的，包括原始文石和丰富的小物种动物群。基于标准化的大规模抽样，我们希望评估三叠纪热带浅水组合的群落内部和群落之间的真实生物多样性、生态复杂性、分类结构和大小分布。将使用与现代和第四纪热带环境组合的比较来评估在2亿多年的进化过程中生物多样性和复杂性的变化。通过与现代样品和代表成岩作用更强烈的(“正常”)化石组合的现有数据集进行比较，可以检验挖掘生物学对保存下来的多样性、大小分布和生态结构的影响。许多在现代热带动物群中高度多样化的类群(如异齿双壳类和新腹足类)并不是在白垩纪之前辐射的。我们的目标是测试在三叠纪是否存在类似的多样性和生态优势的支系，或者多样性是否在更高的类群中分布得更均匀。

The Triassic Cassian Formation yields an exceptionally diverse marine tropical invertebrate fauna offering a largely unbiased assessment of the complexity and biodiversity of early Mesozoic ecosystems. The fauna consist of various assemblages from different localities and paleoenvironments, which vary strongly in terms of diversity and composition. Fossil preservation is usually exceptional including primary aragonite and a rich fauna of small species. Based on standardized large-scale bulk-sampling, we want to assess the true within and between community biodiversity, ecological complexity, taxonomic structure, and size distribution of Triassic tropical shallow water assemblages. Comparisons with assemblages of Recent and Quaternary tropical settings will be used to assess biological changes in diversity and complexity over more than 200 million years of evolution. By comparison with modern samples and existing datasets representing diagenetically more strongly altered (`normal´) fossil assemblages, the effect of taphonomy on preserved diversity, size distribution and ecological structure can be tested. Many of the groups, which are highly diverse in recent tropical faunas (e.g., heterodont bivalves and neogastropods) radiated not before the Cretaceous. We aim at testing if similarly diverse and ecologically dominant clades were present in the Triassic or if diversity was more evenly spread among higher taxa.