Article: Palaeoecology of Appalachian gypidulid brachiopods

Gypidulid brachiopods lived unattached, oriented in a beak-down position aided by weighting of the posterior end of the pedicle valve. This adaptation evolved as a specialization for occupying well reworked and occasionally shifting sand substrates. This sedimentary environment characterizes the open shelf, near wave base in transgressing epeiric seas. The occurrence of Gypidula and its associated faunal community suggest a substrate-salinity control for the analogous Pentamerus Community of Ziegler.