Paleoecologic and paleogeographic factors in the distribution of lower Middle Devonian conodonts from north-central Ohio

Several species of conodonts in the Columbus and Delaware limestones of north-central Ohio are segregated stratigraphically and form associations that correspond fairly well to lithofacies in which they occur. Polygnathus linguiformis, P. angusticostatus, P. angustipennatus, P. intermedius, and Panderodus sp. appear to have been benthic creatures sensitive to substrate texture and energy levels. Other species of Polygnathus may have been benthic, but a nektonic habit is possible for some. Prioniodina tortoides preferred deep-water conditions but was likely nektonic. Simple-cone taxa other than Panderodus and species of Icriodus are ubiquitous and considered to have been shallow-pelagic plankton or nekton. Icriodus orri shows some preference for near-shore environments. Associations similar to some in this area occur in New York, central Ohio, and southwestern Ontario. Endemic forms appear to define a faunal realm limited to the Illinois, Appalachian, and southeastern Michigan basins that is distinct from a realm extending westward and northwestward from the northern to westernmost Michigan Basin. Barriers to intermixing of endemics involved tectonic elements but also hypersalinity and other environmental factors.