The extinct diatom species Thalassiosira Rugulosa (HAJÓS) OGNJANOVA‐RUMENOVA - typification and biostratigraphic significance

Thalassiosira rugulosa (HAJÓS) OGNJANOVA‐RUMENOVA is described and typified as a new fossil diatom combination belonging to the plicated group of the genus Thalassiosira Cl. Until now, these specimens had been identified in a series of biostratigraphic studies conducted in Hungary, Croatia, Serbia, and Romania under the name Coscinodiscus rugulosus Hajós. The presence of loculate areolae ‐ open to the outside by foramina and internally occluded by slightly raised cribrum, as well as two types of processes, both rimoportula and fultoportulae, confirms its assignment to the genus Thalassiosira Cl.