EVALUATING THE EFFECT OF THE CRETACEOUS-PALEOGENE MASS EXTINCTION ON MALACOSTRACAN CRUSTACEANS

The Cretaceous-Paleogene (K-Pg) extinction is one of the most severe mass extinctions in Earth’s history, linked to a meteorite impact near Chicxulub in Mexico and Deccan Trap volcanism in India. Many major groups became extinct (ammonites, belemnites, non-avian dinosaurs, etc.) or experienced major losses in their biodiversity (bivalves, insects, echinoids, etc.). Conversely, decapod crustaceans, major contributors to marine ecosystems since the Mesozoic Decapod Revolution, are thought to have experienced limited losses based on global analyses. Scenarios for this apparent pattern include: (1) decapod diversity was indeed not affected significantly, if at all by the K-Pg event; (2) there was a substantial loss in diversity, but taxon richness rebounded rapidly and was not detectable in coarse global analyses; or (3) uneven sampling has distorted the true signal. Distinguishing between these scenarios has never been carried out thus far by controlled, quantitative sampling on both sides of the K-Pg boundary at sites where both latest Cretaceous (late Maastrichtian) and earliest Paleogene (early Danian) crustacean-bearing sediments are exposed. Previous research has attempted to assess a possible crustacean K-Pg extinction at a more regional scale, but sampling strategies were not provided and/or only very few decapod species were encountered on either side of the boundary, insufficient for detailed comparative analyses. We sampled extensively from two decapod-bearing sites, one far away (~8000 km) from the disaster areas at Stevns Klint (Denmark) and one in Alabama (USA) relatively close (~1200 km) to the impact site. We performed standardized sampling from relatively comparable sediments on both sides of the boundary (fine-grained siliciclastics in Alabama and limestones in Denmark). Specimens from museum collections from those sites augmented the specimens collected during recent our fieldwork. After working out the taxonomy and biostratigraphy, we will assess diversity, abundance, composition, and body size. The preliminary results will be presented during this conference. This research is supported by a 2022 Paleontological Society Arthur James Boucot Research Grant to AAK.