Evolutionary paleoecology of the earliest echinoderms: Helicoplacoids and the Cambrian substrate revolution

Research Article| September 01, 2000 Evolutionary paleoecology of the earliest echinoderms: Helicoplacoids and the Cambrian substrate revolution Stephen Q. Dornbos; Stephen Q. Dornbos 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Search for other works by this author on: GSW Google Scholar David J. Bottjer David J. Bottjer 1Department of Earth Sciences, University of Southern California, Los Angeles, California 90089-0740, USA Search for other works by this author on: GSW Google Scholar Geology (2000) 28 (9): 839–842. https://doi.org/10.1130/0091-7613(2000)28<839:EPOTEE>2.0.CO;2 Article history received: 07 Feb 2000 rev-recd: 05 Jun 2000 accepted: 20 Jun 2000 first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Stephen Q. Dornbos, David J. Bottjer; Evolutionary paleoecology of the earliest echinoderms: Helicoplacoids and the Cambrian substrate revolution. Geology 2000;; 28 (9): 839–842. doi: https://doi.org/10.1130/0091-7613(2000)28<839:EPOTEE>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Bioturbation in neritic siliciclastic settings during the Proterozoic-Phanerozoic transition increased in depth and intensity, causing a change in substrates from the matgrounds characteristic of the Proterozoic to the mixgrounds characteristic of the Phanerozoic. This change in bioturbation increased the water content of surficial layers of sediment and blurred the sediment-water interface, leading to the first appearance of a mixed layer. Development of a mixed layer throughout neritic environments would have had a strong impact on any benthic metazoans, particularly sessile suspension feeders, that were well adapted for survival on relatively unbioturbated Proterozoic substrates. The impact of this substrate transition on benthic metazoans has been termed the “Cambrian substrate revolution.” The unusual Early Cambrian helicoplacoid echinoderms were well adapted for survival on typical Proterozoic-style substrates. The examination of new helicoplacoid specimens collected during this study, combined with extensive study of the rocks in which they are preserved, indicate that helicoplacoids lived as sediment stickers on a muddy substrate that underwent only low to moderate levels of strictly horizontal bioturbation and did not have a mixed layer. The significant increase of bioturbation through the Cambrian in neritic siliciclastic settings is likely to have led to the extinction of the helicoplacoids. Other similarly adapted sessile suspension-feeding echinoderms may have also been driven to extinction by the effects of the Cambrian substrate revolution. The co-existence during the Cambrian of organisms adapted to the variety of substrates characteristic of this transitional period may also have contributed to the high degree of perceived morphological disparity during the Cambrian “explosion.” You do not have access to this content, please speak to your institutional administrator if you feel you should have access.