Meeting Abstract

P2.131  Wednesday, Jan. 5  Further advances in our understanding of the origin and phylogeny of the earliest sea urchins VOLLRATH, K.*; MOOI, R.; San Francisco State University, San Francisco; California Academy of Sciences, San Francisco kvollrath@calacademy.org

Echinoids comprise an ecologically important clade of echinoderms that originated in the upper Ordovician period during the Paleozoic era. Urchins serve as excellent models for analyzing the evolution of novel morphology. Due in part to the sparse fossil record of Paleozoic echinoids, incomplete taxon sampling, and poor understanding of echinoid homologies, there has been much debate and very little conclusive scientific investigation into the Paleozoic origins and subsequent diversification of the Echinoidea. The goal of this study is to provide further insight into the origin of echinoids, and to derive a more complete species level phylogeny encompassing the diversity of Paleozoic forms by using the Extraxial-Axial Theory (EAT) as a foundation for delineating major homologies. By using species descriptions in the primary literature, observing fossil collections, and running phylogenetic analyses to create a more complete phylogeny, we will be better able to determine a supportable evolutionary placement of key taxa such as Bothriocidaris, Bromidechinus, Aulechinus, Eothuria, and Ectinechinus. In addition, the relevance of commonly proposed evolutionarily informative homologies will be assessed and determined in extinct and extant species of echinoids, holothuroids, and ophiocistioids. This study will provide a deeper understanding of the major events in the origin and diversification of echinoids, and uncover the origins and importance of major morphological characters among Paleozoic echinoids, modern echinoids, ophiocistioids, and holothuroids.