We describe the new ichnospecies Oichnus taddeii, a bioerosion trace left by parasitic capulids on fossil brachiopods, prevalently Quaternary Terebratula species. We present the diagnosis of the new ichnospecies and discuss its status. The trace was previously attributed to either Oichnus or Lacrimichnus ichngenera. We provide a statistical assessment of the trace distribution on brachiopod shells, in order to infer the capulid behavior, and the parasitic activity the trace represents.