Cyclotellamima , a Rupelian diatom with cyclotelloid morphology but no fultoportula from the Central Paratethys

A small diatom with cyclotelloid valve morphology was found in Rupelian diatomite outcroppings at sites near three villages in southeastern Poland. Scanning electron microscope-based examination revealed that the diatom does not possess fultoportulae. Instead, short external tubes are part of unusual tubular rimoportulae internally ending in a thick ring surrounding a small opening. Furthermore, the diatom also possesses unique slit-like striae externally covered by an arching canopy consisting of stacked spherules. The diatom does not display any characters that would clearly affiliate it with an already known taxon. Consequently, we propose a new genus (Cyclotellamima) and species (C. bacculata) for this diatom. A rich flora of co-occurring diatoms and other siliceous microfossils suggest that our new species inhabited a coastal marine depositional environment.