Inferring the behaviour of predatory gastropods and their ostracod prey across the Cretaceous–Palaeogene boundary

Abstract Predator–prey dynamics involving ostracod prey across the Cretaceous–Palaeogene (K–Pg) extinction event have not been evaluated rigorously. We studied 3146 Maastrichtian and Danian ostracod specimens from a section in eastern Brazil across the K–Pg boundary. The Maastrichtian assemblage level predation intensity (2.7%) is lower than in the Danian (4.7%). However, the drilling intensity in assemblages immediately above the K–Pg boundary is 0%, perhaps due to abrupt palaeoecological and palaeoenvironmental changes resulting from the K–Pg event. For the Maastrichtian, the dorsal and posterior regions are preferentially drilled, whereas the dorsal and median regions are primarily drilled during the Danian. Variation in Maastrichtian and Danian predation intensities between species (0.0–50.0%) and null model analyses suggest significant prey preference and avoidance, particularly in the Danian, unrelated to prey abundance. Drilling intensities for smooth specimens are significantly greater than for ornamented specimens for the Maastrichtian and the Danian. Finally, Danian drill-hole diameters and predator–prey size ratios are statistically larger than in the Maastrichtian, suggesting predatory gastropods were larger after the boundary, also relative to their prey. We conclude that predator–prey dynamics were affected by the K–Pg extinction event.