New insights on the Paleogene dinoflagellate cyst genera Enneadocysta and Licracysta gen. nov. based on material from offshore eastern Canada and southern Argentina

Abstract

Enneadocysta is a biostratigraphically important Paleogene dinoflagellate cyst genus. Its original interpretation as a partiform gonyaulacoid (thus belonging to the gonyaulacalean suborder Cladopyxiineae) was based on the presence of two antapical processes. Another Paleogene genus, Areosphaeridium, is similar, at least superficially, to Enneadocysta, but has a single antapical process, placing it in the sexiform gonyaulacalean suborder Gonyaulacineae. The morphology of a new species of Enneadocysta from offshore eastern Canada, Enneadocysta magna, shows that the two antapical processes of the genus (unlike processes reflecting other plate series) are penitabular, not mesotabular, and indicates that the genus is gonyaulacinean, not cladopyxiinean. This new interpretation, as well as new material from southern Argentina, confirms the generic assignment of the Southern Hemisphere species Enneadocysta dictyostila (emended) and a new species, Enneadocysta brevistila. A new genus and species, Licracysta corymbus, from offshore eastern Canada is intermediate in morphology between Enneadocysta and Cleistosphaeridium and strongly suggests an assignment for all three genera to the gonyaulacinean family Areoligeraceae. The new combination Licracysta? semicirculata is questionably proposed, and the descriptive terms licrate, dolabrate, entire clypeate, ragged clypeate, intratabular, mesotabular, obtabular, contabular and nontabular are either proposed as new or reviewed.