Systematics and Comparative Ontogeny of Silicified Late Cambrian and Early Ordovician Trilobite Faunas of the Great Basin: Bridging a Phylogenetic Gap.

9973065Westrop寒武纪与后寒武纪三叶虫之间明显的系统发育差距一直被认为是该类群历史上的基本问题之一。它阻碍了对奥陶纪海洋群落大重组期间新三叶虫群起源的清晰理解。通过比较，我们对寒武纪后三叶虫主要类群之间的关系有了很好的认识，这是通过枝源分类技术的应用，特别是通过硅化物质个体发育的比较研究实现的。对寒武纪三叶虫的类似处理由于硅化动物群的缺乏而受阻。本课题将研究大盆地新发现的、多样的寒武纪硅化动物群。它们有可能彻底改变我们对寒武纪和后寒武纪三叶虫之间关系的理解，并最终将奥陶纪辐射置于其适当的系统发育背景中。

9973065Westrop The apparent phylogenetic gap between Cambrian and post-Cambrian trilobites has long been recognized as one of the fundamental problems in the history of the group. It prevents a clear understanding of the origination of new groups of trilobites during the major reorganization of marine communities that took place during the Ordovician. By comparison, relationships between major groups of post-Cambrian trilobites are well understood, and this has been achieved by the application of cladistic techniques and, especially, by comparative studies of ontogenetic development of silicified material. Similar treatment of Cambrian trilobites has been hindered by the scarcity of silicified faunas. This proposal will study newly discovered, diverse Cambrian silicified faunas of the Great Basin. They have the potential to revolutionize our understanding of the relationships between Cambrian and post-Cambrian trilobites, and to finally place the Ordovician radiation in its proper phylogenetic context.