Phylogenetic implications of the Protocrinoida: Blastozoans are not ancestral to crinoids |
| |
Authors: | Thomas E Guensburg James Sprinkle |
| |
Institution: | aSciences Division, Rock Valley College, 3301N Mulford Road, Rockford, IL 61114, USA;bDepartment of Geological Sciences, Jackson School of Geosciences, University of Texas 1, University Station, Austin, TX 78712-0254, USA |
| |
Abstract: | A traditional, widely cited hypothesis for over a century posits the origin of the crinoids from blastozoans. The blastozoan hypothesis is contradicted by the discovery of a new crinoid order, the Protocrinoida. Protocrinoids exhibit many traits that are consistent with a basal crinoid phylogenetic position, but inconsistent with a blastozoan ancestry. Protocrinoids are among the oldest crinoids and are therefore stratigraphically correctly placed. The blastozoan hypothesis in contrast, relies on putative homologies between blastozoans and crinoids taken from taxonomically and stratigraphically disparate representatives of both groups; these disparities indicate homoplasy rather than propinquity of descent. Data supporting these ideas are reviewed here. These findings reinforce insightful observations made by Georges Ubaghs decades ago with less data. |
| |
Keywords: | Crinoids Blastozoans Echinoderms Homoplasy RhombiferansMots clé s: Crinoï des Blastozoaires É chinodermes Homoplasie Rhombifè res |
本文献已被 ScienceDirect 等数据库收录! |
|