HABITAT AFFINITY OF LINGULID BRACHIOPODS THROUGHOUT THE PHANEROZOIC AS A PROXY FOR OPPORTUNISTIC “DISASTER TAXA” BEHAVIOR

Lingulid brachiopods originated in the Cambrian, and have survived all five first-order mass extinction events. The genus Lingula, specifically, is widely accepted to be opportunistic, and acts as “disaster taxa” following the end-Permian mass extinction. However, this study aims to document this opportunistic behavior throughout several other Phanerozoic extinction events and biotic crises in Lingula and other lingulid taxa. We quantify affinity of lingulid brachiopod taxa in terms of depth, grain size, and substrate lithology preference across Phanerozoic Periods to track changes in their ecological tolerance. Habitat affinity was calculated per time bin using both the standardized relative affinity method and the binomial test, and was based on a dataset of global fossil occurrences reported in the Paleobiology Database (PBDB). The affinity for deep vs. shallow, carbonate vs. siliciclastic and fine vs. coarse grained substrate was compared for each time bin. Standard relative affinity for a particular habitat was calculated for the family Lingulidae relative to all other brachiopods. The binomial test was used to calculate the habitat affinity for the family Lingulidae relative to the total available habitats per time bin, as calculated from total PBDB collections.

Lingulid brachiopods experience a general proportional change in their preferred habitat during the Mesozoic from largely shallow, to having no preference, or a deep water preference. There is also a shift from siliciclastic to carbonate substrate affinity during this time. Additionally, brachiopods belonging to the family Lingulidae also show a shift from having no substrate affinity to having a preference during the Mesozoic. This shift in substrate affinity suggests that linugulid brachiopods adapted to environmental and ecological stresses, and were able to occupy new substrates as a mechanism for survival following extinction events. The opportunistic behavior and overall ability of lingulid brachiopods to adapt to living in a new substrate could provide an explanation for the longevity of lingulid brachiopods, and for their success following extinction events.