DAVEYA-BORESPHAEIA GEN ET SP-NOV, A VALID NAME FOR THE DINOFLAGELLATECYSTS GONYAULACYSTA SP-A DAVEY 1979 AND SP-B DAVEY 1982, AND SOME REMARKS REGARDING THE FORMAL STATUS OF MUDERONGIA-BREVISPINOSA IOSIFOVA 1996

This taxonomic note formally describes the two taxa cited in the liter ature as ''Gonyaulacysta sp. A DAVEY 1979'' and ''Gonyaulacysta sp. B DAVEY 1982'' under the single name Daveya boresphaera gen. et sp. nov. Based on stratigraphical and palaeoecological considerations, both ta xa are considered herein to express two phenotypic ornamental variatio ns (formae A and B) of the same motile form. Daveya gen. nov. shows a gonyaulacacean paratabulation pattern and an S-type ventral organisati on, combined with an A/ai arrangement. The parasuture 4'/1' is clearly marked, a feature rarely observed within species displaying this type of ventral arrangement. A typical adherent operculum (P-3.), a thick, spongious, undifferentiated autophragm and a typical spherical shape distinguish Daveya gen. nov. from the genus Gonyaulacysta DEFLANDRE 19 64 emend. SARJEANT 1982, Morphological characteristics of Daveya gen. nov. dictate its inclusion in the Gonyaulacoideae subfamily. The type species, Daveya boresphaera sp, nov., is a useful marker for the Upper Ryazanian of the European boreal province (British Isles, offshore No rth Sea, Denmark and Norwegian Sea). With regard to palaeoecological c onsiderations already mentioned above, the new species Muderongia brev ispinosa IOSIFOVA 1996 is considered to be a taxonomic junior synonym of Muderongia longicorna MONTEIL 1991, which is emended.