A case of intense predatory drilling of brachiopods from the Middle Miocene of southeastern Poland

The documentation of biotic interactions in the fossil record is important not only to understanding the earth’s paleoecological history, but also to testing the evolutionary role of such interactions. Drill holes in invertebrate shells provide one of the most direct and easily interpretable signals of such interactions and the documentation and interpretation of the spatio-temporal patterns of drill hole frequencies in a variety of invertebrate taxa has been the subject of extensive paleontological research. For brachiopods, the most recent summaries suggest that the record of drill holes extends back to the early Paleozoic, shows an increase in the Devonian, and remains highly variable through the rest of the Paleozoic. There are few reported cases of drilled brachiopods from the Mesozoic, although in those few instances on record, frequencies can be as high as in the Paleozoic. To date, only a few drilled brachiopods have been reported from the record of the Cenozoic. Here, we report on over 500 drilled brachiopod specimens, constituting 39.9% of all brachiopod shells examined, from a single Middle Miocene locality in southeastern Poland. This drilling frequency is high when compared to two additional Middle Miocene localities in Poland, where frequencies are 2.0% and 3.7%. These results suggest that (1) Cenozoic brachiopods were predated upon by drilling gastropods, often with high intensities, and (2) in the Miocene, drilling frequencies could be highly variable, even at proximate localities. The largely unexplored record of brachiopod drill holes across the late Mesozoic and Cenozoic could provide additional evidence for the Mesozoic Marine Revolution.