Brachiopod morphology, life mode, and crushing predation in the Ordovician Arnheim Formation, Kentucky, USA

Abstract

Predation on ancient shelled prey is an often-studied topic in paleoecology, but the early Paleozoic and the brachiopods that dominated the seafloor at that time are relatively underrepresented in the predation literature. We assessed predatory repair scar frequencies among the brachiopod genera from the Early Richmondian (Late Ordovician) Oregonia Member (Arnheim Formation) near Flemingsburg, Kentucky. We found higher repair frequencies on the concavo-convex Rafinesquina and Leptaena relative to the bi-convex genera. There were no trends in repair frequency through the stratigraphic section and no relationships between repair frequency and community diversity metrics. It is possible that concavo-convex brachiopods’ flat shape, thin shell profile, and free-lying (no pedicle attachment) lifestyle made them more likely or appealing targets of Ordovician crushing predators. It is also possible that concavo-convex brachiopods were better suited to survive crushing attacks than biconvex taxa. We also found differences in shell ornament that may influence the visibility of repair scars.