Bioerosion in Pliocene to Late Holocene tests of benthic and planktonic foraminiferans, with a revision of the ichnogenera Oichnus and Tremichnus

An ichnotaxonomic revision is given of the two ichnogenera Oichnus Bromley 1981 and Tremichnus Brett 1985. The following ichnotaxa are retained: O. simplex, O. paraboloides and O. ovalis. Abandonment of T. paraboloides, T. cysticus, T. minutus, T. puteolus and Tremichnus isp. aff. T. puteolus is proposed herein. Several specimens of O. simplex and O. paraboloides are present in the studied tests. Bioerosional structures have been observed in more than 600 out of 30,000 tests of Pliocene to late Holocene benthic and planktonic foraminiferans. A new ichnogenus, Stellatichnus igen, nov., is proposed herein to include star‐shaped holes. This ichnogenus comprises one ichnospecies, Stellatichnus radiatus isp. nov. Its overall shape seems to be related to substrate thickness. Three new ichnospecies of Oichnus are also defined. O. coronatus isp. nov. is distinguished by a halo of surficially etched substrate, but is otherwise similar to O. simplex. O. asperus isp. nov. is characterized by openings with irregular elongate‐oval outlines. The distinctive feature of O. gradatus isp. nov. is its two interconnected subcylindrical components. Dipatulichnus igen. nov., which contains D. rotundus isp. nov., comprises pairs of circular holes. These bioerosional structures are interpreted as representing the ethologic categories praedichnia and domichnia. Biological affinities of the tracemakers are unknown.