The fossil record can illuminate factors that contribute to extinction risk during times of global environmental disturbance; for example, inferred thermal tolerance was an important predictor of extinction during several mass extinctions that corresponded with climate change. Additionally, members of geographically isolated biotas may face higher risk because they have less opportunity to migrate to suitable climate refugia during environmental disturbances. Here, we investigate how different types of risk intersect in the well-preserved brachiopod fauna of the Appalachian Foreland Basin during the two pulses of the Frasnian–Famennian mass extinction (Late Devonian, ~ 372 Ma). The selectivity of extinction is consistent with climate change (cooling) as a primary kill mechanism in this fauna. Overall, the extinction was mild relative to other regions, despite the many endemic species. However, vulnerable taxa went extinct more rapidly, during the first extinction pulse, such that the second pulse was insignificant. These results suggest that vulnerable taxa in geographically isolated biotas face heightened extinction risk at the initiation of environmental stress, but that taxa in other regions may eventually see elevated extinction risk if environmental stress repeats or intensifies.

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Skeletobionts, organisms that attach to or bore into the skeleton of a host, provide a useful system to observe biological interactions over geological timescales. We examined skeletobionts on brachiopod hosts from a stratigraphic section in western New York State that spanned the Lower Kellwasser and Upper Kellwasser events, the two pulses of the Frasnian–Famennian (Late Devonian) mass extinction. The fossils are largely preserved as molds, and even endoskeletobiont borings are often visible with minimal preparation. At least seven major groups of skeletobiont are present including microconchids, stenolaemate and ctenostome bryozoans, hederelloids, and various borings attributed to sponges. The total frequency of skeletobiosis declined significantly across the first extinction pulse (Lower Kellwasser Event), and relative abundance patterns shifted, although the biotic and/or abiotic drivers of these changes require further study. Multivariable logistic regression indicates that large host body size was a strong and consistent predictor of skeletobiosis. Endoskeletobionts were more common in coarser lithologies, reflecting either an ecological preference for sands over muds or a bias against preservation in mudstones. Endoskeletobionts were also more common on ribbed/costate host shells.