New Eocene organic-walled phytoplankton taxa from the Norwegian North Sea, and their regional biostratigraphical application

Biostratigraphical study of Eocene deposits from offshore wells in the Norwegian and U.K. continental shelf areas has allowed the description and age-range calibration of new species of organic-walled phytoplankton. This study formally describes the following new dinoflagellate cyst species: Areosphaeridium martinpearcei, Areosphaeridium truncatum, Cooksonidium prolixum, Cribroperidinium neoreticulatum, Eatonicysta filamentosa and Lentinia laevigata, and the subspecies Spiniferites manumii pumilus. A new species of the algal form genus Fromea is described, Fromea crinita. An acritarch, Orbitalaria costata gen. et sp. nov. is also described. The species Stephodinium? parva, which has previously been tentatively assigned to the dinoflagellate cyst genus Stephodinium, is transferred to this new acritarch genus, Orbitalaria parva (De Coninck 1986) comb. nov. Furthermore, sporadic occurrences of the marker dinoflagellate cysts Impagidinium obscurum and Spiniferites rhomboideus (Paleocene, Thanetian), are recorded from Eocene strata, significantly extending their previously established stratigraphical ranges.