Population paleoecology and comparative taphonomy of two edrioasteroid (echinodermata) pavements: Upper ordovician of kentucky and Ohio
Titel:
Population paleoecology and comparative taphonomy of two edrioasteroid (echinodermata) pavements: Upper ordovician of kentucky and Ohio
Auteur:
Meyer, David L.
Verschenen in:
Historical biology
Paginering:
Jaargang 4 (1990) nr. 3-4 pagina's 155-178
Jaar:
1990
Inhoud:
Two strophomenid brachiopod shell pavements bearing abundant edrioasteroid epizoans occur stratigraphically within the top 4.5 m of the Corryville Formation (Upper Ordovician, Maysvillian) in Boone County, Kentucky, and Hamilton County, Ohio. Both assemblages are dominated by Isorophus cincinnatiensis and contain Carneyella pilea and Streptaster vorticellatus as lesser constituents. Pedicle exterior valves of Rafinesquina “alternata”; are the preferred substratum for all species at both sites, but the Kentucky population occurs mainly on unabraded, articulated shells and the Ohio population occupies abraded, disarticulated shells. The Kentucky population includes a greater size range of Isorophus (at least three cohorts) than the Ohio population (at least two cohorts), suggesting a greater time span of colonization for the Kentucky site. Host shells from Kentucky have anterior-posterior axes strongly aligned NE-SW whereas the Ohio shells are unoriented. Isorophus in Kentucky show a preference for the anterior margin of the Rafinesquina pedicle exterior valve, whereas Isorophus in Ohio show no preferred location on host shells. The Kentucky edrioasteroids are inferred to have attached to mainly live Rafinesquina in brachial-valve-up position. Host shells were inverted and oriented by a NE-SW storm surge, then buried rapidly. Ohio edrioasteroids occupied mainly dead, already inverted host shells not oriented by storm surge possibly because of their more downslope (distal) location. Comparative taphonomic relationships between the two coeval populations are consistent with a model of proximal to distal distribution along a gentle shallow subtidal N-S paleoslope subject to episodic storm activity.
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