Taxonomic revision of some Cretaceous–Cenozoic spiny organic-walled peridiniacean dinoflagellate cysts

In the marginal marine Eocene sediments recovered on Ocean Drilling Program Leg 189, offshore Tasmania, the dominant peridiniacean dinoflagellate cysts in many samples are spiny forms with generally steno- isodeltaform 2a plates assigned to Spinidinium, Vozzhennikovia and allied genera. Many of the species are endemic Antarctic taxa. Based on new observations we propose taxonomic revisions on the basis of the distribution of the ornamentation and the shape of the second anterior intercalary (2a) plate, as well as the nature of archeopyle formation, which always involves the 2a plate. We regard Magallanesium and Volkheimeridium to be taxonomic junior synonyms of Spinidinium. We erect the genus Moria and the species Moria zachosii, Spinidinium schellenbergii, Vozzhennikovia stickleyae and Vozzhennikovia roehliae. We also propose a new morphological term, “proximosutural”. The refinement of these taxonomic concepts and the addition of new taxa will enable spiny peridinaiacean dinocysts to be more effectively used in biostratigraphic and paleoenvironmental interpretations.