New insights on the morphology and occurrence of the Palaeogene dinoflagellate cyst speciesDuosphaeridium rugosumand on the taxonomic affinity of the genusDuosphaeridium

The extinct organic-walled dinoflagellate cyst Duosphaeridium rugosum was first described from the Paleocene (Danian) of the southern USA. It has since been documented at several other localities around the world. Well-preserved specimens from the Danian of the Dakhla Formation in the Dababiya Corehole in southern Egypt, illustrated by light and scanning electron microscope images, reveal new morphological details, most notably parasutural...