TRACKING THE ECOLOGICAL TOLERANCE AND OPPORTUNISTIC BEHAVIOR OF LINGULA THROUGHOUT THE PHANEROZOIC USING SUBSTRATE AFFINITY METRICS

The genus Lingula originated in the Cambrian, has survived all five first-order mass extinction events and is often referred to as a “living fossil.” Lingula is widely accepted to be opportunistic, and acts as a “disaster taxon” following the end-Permian mass extinction. However, this study aims to quantify and document the ecological tolerance and behavior of Lingua for all five first-order mass extinction events. We quantify affinity of lingulid brachiopod taxa in terms of depth, grain size, and substrate lithology preference across each Epoch within the Phanerozoic 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 was calculated for each habitat to compare the substrate preferences of Lingula with other benthic marine fauna, including rhynchonelliform brachiopods. Habitat affinity was also determined relative to the disaster taxa Claraia, Eumorphotis, Promyalina, and Unionities throughout the Permian and Triassic. The binomial test was used to calculate the habitat affinity for Lingula relative to the total available habitats per time bin, as calculated from total PBDB collections. The binomial test was used to standardize the Lingula habitat affinity with all the other occurrences within each timebin to ensure that the affinity is not an artifact of a stratigraphic facies bias.

Overall, Lingula exhibits a shift in ecological behavior following each major extinction event towards a more generalist life strategy. Lingula was found to have a higher ecological tolerance and was overall more generalist than rhynchonelliform brachiopods. Additionally, Lingula was more generalist and opportunistic than the disaster taxa from the EPME. Therefore, the opportunistic behavior associated with Lingula could provide an explanation for its “success” following extinction events, and longevity relative to other disaster taxa and brachiopods.