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

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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.