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

三叠纪Cassian组产生了异常多样的海洋热带无脊椎动物群，为中生代早期生态系统的复杂性和生物多样性提供了基本上公正的评估。动物群由来自不同地点和古环境的各种组合组成，在多样性和组成方面差异很大。化石保存通常是例外，包括初级文石和丰富的小物种动物群。 基于标准化的大规模批量采样，我们要评估真正的内部和之间的社区生物多样性，生态复杂性，分类结构，和大小分布的三叠纪热带浅水组合。近期和第四纪热带环境组合的比较将被用来评估生物多样性和复杂性的变化超过2亿年的演变。通过与现代样品和现有的数据集代表成岩作用更强烈改变（“正常”）的化石组合相比，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群体（例如，异齿类、双壳类和新腹足类）在白垩纪之前没有辐射。我们的目的是测试，如果类似的多样性和生态优势的分支存在于三叠纪，或者如果多样性更均匀地分布在更高的类群。

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.