Early Fossil Record and Evolution of Echinoderms and Octocorals - evidences from the Yangtze Platform, China

点击翻译按钮获取中文摘要

Only few marine animals are immediately recognizable as echinoderms: the fivefold symmetry of a sea urchin or starfish is striking, and this pentaradiate form sets them apart from their bilaterally symmetrical relatives. The echinoderm skeleton is equally distinctive, being made of calcitic plates with a typical microstructure (stereom). But representatives of the Echinodermata have not always possessed these features, and exploring their early history remains highly controversial. The Proterozoic origin of the modern echinoderm bauptan, especially of the free-living representatives (Eleutherozoa), is unclear. Similar conditions have been found within the anthozoan cnidarians. The fossil record of octocorals traces back into the Neoproterozoic time with pennatulid-like organisms in various Ediacara biota; but relationships of these taxa are still under debate. It is assumed that the Precambrian stem group of echinoderms were probably comprised of nonpentaradial or non-radial organism lacking calcitic stereom plates. In contrast to the far more common opinion that the Pennatulacea are the first representatives of the Octocorallia, it is assumed that gorgonaceous and alcyonacean octocorals are one of the first octocorallian cnidarians, and the modern pennatulacean octocorals are highly evolved organisms, first known since the Mesozoic. The Yangtze Platform is a worldwide unique location where we have the chance to solve problems and questions of early metazoan radiation and related biomineralisation. Based on new and not yet applied micropalae onto logical extraction methods and through the combination of macro- and micropalaeontological investigations we plan to fill a gap in the incomplete and poorly understood early fossil record of echinoderms and octocorals.