Unveiling the Permian and Triassic record of drilling predation on ostracods

Drill holes are relatively common trace fossils on post-Paleozoic ostracods (especially from the Cretaceous onwards) and usually ascribed to predation by Muricidae and Naticidae gastropods. In the last few decades, increasing reports of these marks on Late Paleozoic and Early Mesozoic ostracods appeared in the literature. In this paper, we review the drill holes on marine and mixohaline ostracods with emphasis on the Permian and Triassic intervals, based on a detailed analysis of their published records, as well as new specimens and data.
Based on ichnological principles, analyzes of several types of marks observed on ostracodswere carried out to distinguish holes caused by predation on live individuals from the effects of dissolution and post-mortem bioerosion. The twenty-two marks identified as drill holes in this work are classified into nine types, ranging from Kungurian-Roadian to Rhaetian in age. The diversity of drill hole patterns supplies new evidence that the end-Permian biotic crisis influenced not only the global ostracod diversity, but also the trophic interactions. In the Late Triassic, the drilling predators were already deterred by increased thickness or complex ornamentation of bairdiid shells. Although the data do not permit precise identification of drilling predators, it is assumed that different animal groups might have performed this action throughout geologic time, due to the diversity of paleoenvironments and broad chronostratigraphic occurrence of drill holes analyzed. Potential drilling predators both in marine and mixohaline (paleo)environments are briefly discussed.