Epicontinental seas versus open-ocean settings: the kinetics of mass extinction and origination.

Environmental perturbations during mass extinctions were likely manifested differently in epicontinental seas than in open-ocean-facing habitats of comparable depth. Here, we present a dissection of origination and extinction in epicontinental seas versus open-ocean-facing coastal regions in the Permian through Cretaceous periods, an interval through which both settings are well represented in the fossil record. Results demonstrate that extinction rates were significantly higher in open-ocean settings than in epicontinental seas during major mass extinctions but not at other times and that origination rates were significantly higher in open-ocean settings for a protracted interval from the Late Jurassic through the Late Cretaceous. These patterns are manifested even when other paleogeographic and environmental variables are held fixed, indicating that epicontinental seas and open-ocean-facing coastlines carry distinct macroevolutionary signatures.