Middle and Upper Ordovician Symmetrical Univalved Mollusks (Monoplacophora andBellerophontina) of the Cincinnati Arch Region

摘要

The purpose of the paper is to discuss the taxonomy, functional morphology,paleoecology, biostratigraphy, and phylogenetic relationships of the Middle and Upper Ordovician Monoplacophora and bellerophontacean Gastropoda of the Cincinnati arch region in central Kentucky, Tennessee, southwestern Ohio, and southeastern Indiana. The most recent comprehensive treatment of these faunas was a monograph by Ulrich and Scofield in 1897. Although fossil monoplacophorans and gastropods can be locally common elements of North American Ordovician faunas, they have received almost no modern study. The original aragonitic skeletons of these mollusks generally were dissolved in early diagenesis, and therefore most known specimens are preserved as internal molds.