Tetrentactinia barysphaera Foreman, 1963: skeletal structure and age of a biostratigraphically important Famennian (Upper Devonian) radiolarian from the Ohio Shale, USA

Abstract

Tetrentactinia barysphaera Foreman, 1963 is a very characteristic Famennian (Upper Devonian) radiolarian species from the Huron Member of the Ohio Shale of North America. Its skeletal structure shows a massive, double-layered shell with main spines constructed from radial beams and concentric bars over a primary ray as the core. The species is common in limestone concretions at the type locality Milan, Ohio, associated with a diverse radiolarian fauna of predominantly spherical spumellarian forms, but has also been recorded from the Russian platform. It may be highly useful as an index species for the mid-Famennian time interval as it is one of the few spumellarians that is easily recognized and differentiated in the fauna.