Abstract

The Fairview and McMillan formations of the Cincinnati region, the reference standard for the North American Maysville stage (Upper Ordovician), have yielded a large collection of conodont elements, referable to 29 species, distributed among 18 genera. Fourteen species are known to range through the Eden, Fairview, and McMillan formations; most of these are represented as well in late Mohawkian and Trentonian strata in the midcontinent province of North America, and several continue into the Richmond group. Three species in the Fairview fauna occur also in the Eden, but do not range above the Fairview locally; 7 species are restricted to the Fairview. Four species, introduced locally in late Eden or early Fairview strata, continue into the McMillan, which otherwise contains a reduced fauna of long-ranging midcontinent species. The presence of Ambalodus, Amorphognathus, and Belodina in Eden and Fairview strata, but not above them, suggests that the Orchard Creek shale of Missouri, the pre-upper Brainard Maquoketa shale of Iowa, and the Maravillas formation of Texas (which have all yielded representatives of these genera) are Maysville in age, or older. Four species (Eoligonodina fairmountensis, Oulodus casteri, Prioniodina velicuspis, and Zygognathus maysvillensis) are described for the first time.

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