Niels E. Poulsen

Jurassic dinoflagellate cyst biostratigraphy of the Danish Subbasin in relation to sequences in England and Poland; a preliminary review

Abstract A palynological study of marine Jurassic deposits of the Danish Subbasin has identified most of the zones and subzones of the dinoflagellate cyst biozonation established in the British Isles. One new subzone of the Mancodinium semitabulatum Zone, the Parvocysta nasuta Subzone (latest Early Jurassic to earliest mid-Jurassic), is proposed. The Early Jurassic zonal scheme is correlated with existing miospore and ostracod zonations. Middle Jurassic strata in Denmark are mainly non-marine. Study of Late Jurassic ammonite-dated samples from Poland has provided additional control on the correlation of the Danish dinoflagellate cyst zonal scheme. Dinoflagellate cysts in the Volgian Scythicus Zone of Poland allow reliable correlation of this zone with the Portlandian Albani Zone of England and Denmark. One new species of dinoflagellate cyst, Nannoceratopsis ridingii , is described.

A TAXONOMIC STUDY OF THE DINOFLAGELLATE CYST MUDERONGIA SIMPLEX ALBERTI 1961 AND RELATED SPECIES

Abstract Following a restudy of the type material of Muderongia simplex Alberti 1961, this species and the informally‐named Volgian morphotype Muderongia sp. A of Davey (1979) are deemed to be unequivocally conspecific. They both have angular endocysts, the extremities of which extend into the pericystal horns, thereby engendering a cornucavate cyst organisation. The specific diagnosis of Muderongia simplex is emended to note this morphologic phenomenon. The distinctive Lower Cretaceous (Ryazanian to Hauterivian‐Barremian) circumcavate representatives of Muderongia which have been extensively referred to as Muderongia simplex in the literature are assigned to the new species Muderongia endovata. The distinction between the genera Muderongia and Phoberocysta is maintained, contrary to a recent synonymisation.

Gonyaulacysta jurassica desmos, a new subspecies of dinoflagellate cyst from the early Oxfordian (Late Jurassic) of Northwestern Europe and East Greenland

Abstract In the emendation of Gonyaulacysta jurassica (Deflandre 1938) Norris & Sarjeant 1965 by Sarjeant (1982), a variety of G. jurassica jurassica near the range base was described but not formally named. This variety, herein named G. jurassica desmos subsp. nov., is considered to be of stratigraphical utility because it is confined to the early Oxfordian. Gonyaulacysta jurassica jurassica is emended, and geographic variation in the stratigraphic ranges of the three subspecies of G. jurassica is discussed.