Predatory drill holes in Ostracoda: An overview of patterns in the fossil record

The fossil record is an outstanding data source for understanding predator-prey interactions. Although drill holes are relatively well studied in calcareous metazoans, their record in ostracods is sparse compared to other taxa (e.g., gastropods and bivalves). Based on an extensive literature review, we have compiled the Phanerozoic record of drill holes in Ostracoda to identify patterns in predator-prey interactions in these crustaceans. Our results show that most research has is on Cenozoic material and is concentrated in Europe, especially in Spain and Italy. Although drilling predation on ostracods is presentd since the Silurian, drilling intensity appears quantifiable and more common from the Cretaceous onwards. Drill holes are predominant in the central region of carapaces in the Cenozoic and are identified as the ichnospecies Oichnus paraboloides and Oichnus simplex. Compared to Mesozoic and Paleozoic records, the predator-prey size ratio increased dramatically after the K-Pg boundary. Null model analysis suggests that some ostracod genera were preferentially preyed on, unrelated to their relative abundance. Our data demonstrate that the drilling intensity was lower in the Mesozoic than the Cenozoic, a pattern observed for the first time in Ostracoda. Finally, our paper also identifies various knowledge gaps and opportunities to further study predation in ostracods.