A small yet occasional meal: predatory drill holes in Paleocene ostracods from Argentina and methods to infer predation intensity

Ostracods are common yet understudied prey in the fossil record. We document drill holes in Paleocene (Danian) ostracods from central Argentina using 9025 specimens representing 66 species. While the assemblage-level drilling percentage is only 2.3%, considerable variation exists within species (0.3–25%), suggesting prey preference by the drillers. This preference is not determined by abundance because no significant correlation is found between species abundance and drilling percentages. Seven methods were used, some of which are new, to quantify drilling percentages for the abundant and commonly drilled Togoina argentinensis. The obtained range from 9.9 to 14.6% suggests that drilling percentages are fairly insensitive to the method used, implying that comparisons across studies appear possible. Using this knowledge, the Cretaceous-Paleogene mass extinction had limited effect on drilling intensity in ostracod prey. The cylindrical (Oichnus simplex) and parabolic (O. paraboloides) dril...