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

三叠纪Cassian组产生了异常多样化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很大程度上公正的评估。动物群由来自不同地区和古环境的各种组合组成，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。基于标准化的大尺度体样，我们希望评估三叠纪热带浅水群落内部和之间的真实群落多样性、生态复杂性、分类结构和大小分布。与近代和第四纪热带环境组合的比较将用于评估2亿多年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的（“正常”）化石组合的现有数据集进行比较，可以测试埋藏对保存的多样性、大小分布和生态结构的影响。许多在最近的热带动物群中高度多样化的类群（例如，异齿双壳类动物和新胃足类动物）在白垩纪之前就已经出现了。我们的目的是测试三叠纪是否存在类似的多样性和生态优势枝，或者多样性是否更均匀地分布在更高的分类群中。

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.