Rare signs of predation on rhynchonellate brachiopods in the early Katian (Late Ordovician) of northern Estonia

Oichnus simplex Bromley, 1981 occurs in Clinambon sp. and Ilmarinia dimorpha Öpik, 1934 from the lower Katian of northern Estonia. Oichnus paraboloides Bromley, 1981 was found in 1.9 % of all Porambonites sp. specimens. Shell repair occurs in Hesperorthis? sp., Pseudostrophomena sp., Holtedahlina sakuensis Oraspõld, 1956, and Hedstroemina oanduensis Oraspõld, 1956. The scars in rhynchonellates most closely resemble Caedichnus lunaris Nicol & Leighton, 2023 and are assigned to this ichnospecies. The predator was not strong enough or large enough to crush the entire shell and consume the whole soft body of the brachiopod. Instead, it broke pieces away from the anterior commissure and consumed most anterior parts of the mantle without killing the brachiopod. Multiple bites at the shell anterior found in Pseudostrophomena sp. and Hedstroemina oanduensis indicate that these brachiopod species were certainly within normal parameters of prey for the predator. The drilling frequency (1.9%) of Pormabonites in the Katian is above 1% but still low enough to fit with the idea of brachiopods as victims of mistaken or opportunistic attacks by predators targeting other organisms. The high drilling frequency of Ilmarinia (18.2 %) could be due to a non-representative sample size and post-mortem bioerosion.