Crypto-helical body plan in partially disarticulated gogiids from the Cambrian of South China |
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| Institution: | 1. State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China;2. School of Earth Sciences, Ohio State University, Columbus, OH 43210, USA;3. College of Resource and Environment Engineering, Guizhou University, Guiyang 550003, China;4. Bureau of Land and Resources, Qiandongnan Autonomous Prefecture of Guizhou Province, Kaili 556000, China |
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| Abstract: | All living echinoderms have a pentaradial symmetry that is unique within the Bilateria. However, the Cambrian origin of echinoderm radial/pentaradiate symmetry is a long-standing problem. During the Cambrian (542–488 Ma), gogiids were the most common stalked echinoderm characterized by an “irregularly” plated body. Based on recently discovered material from the Balang Formation (Cambrian Series 2), eastern Guizhou, China, three unusual, partially disarticulated specimens of Guizhoueocrinus have clear evidence for a helical body plan. This helical plating is only evident in partially disarticulated specimens, thus a crypto-helical body construction is present. Crypto-helical construction in a gogiid raises the possibility of a phylogenetic connection among helicoplacoids, gogiids, and Helicocystis. The crypto-helical body construction may be an important evolutionary innovation among pre-radiate echinoderms. |
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| Keywords: | Cambrian explosion Macroevolution Echinodermata Taphonomy |
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