A reappraisal of the cainozoic dinoflagellate cyst “ Hystrichosphaeridium” choanophorum deflandre et Cookson 1955

Abstract

Palynological research on the Miocene Blue Clay of Malta and on Miocene sediments from the southwestern continental shelf of the United Kingdom has led to a reappraisal of the dinoflagellate cyst species “ Hystrichosphaeridium” choanophorum Deflandre et Cookson 1955. A precingular archeopyle (Type P) is described for the cyst, which precludes its assignment to the cyst genus Hystrichosphaeridium Deflandre, and a paratabulation of pr, 4′, 6″, 0–6c, 6′″, 1p, 1″″ is demonstrated, from a process formula of pr, 4′, 6″, 0–6c, 5′″, 1p, 1″″. Considerable variation in the morphology of the distal tips of the processes is also noted and illustrated.