English Jurassic dinoflagellate cysts and acritarchs: A reexamination of some type and figured specimens

As a consequence of advances in knowledge of the morphology and relationships of dinoflagellate cysts and acritarchs and increasing sophistication in optical equipment, earlier descriptions of dinoflagellate cysts and acritarchs are in general obsolete; re‐descriptions are necessary to furnish fuller morphological information. In this paper are given the results of a reexamination of holotypes or figured specimens of 26 species of dinoflagellate cysts and 3 species of acritarchs, all from the Middle to Upper Jurassic (lower Callovian to Kimmeridgian) of England. The new species Gonyaulacysta setcheyensis and the new combination Acanthaulax downiei (Sarjeant) are proposed; two species, Heslertonia teichophera (Sarjeant) and Meiourogonyaulax? acanthosphaera (Sarjeant), are generically reassigned and emended; and the diagnosis of Leptodinium mosaicum (Downie) is emended. It is demonstrated that the genera Netrely‐tron Sarjeant and Paranett‐elytron Sarjeant do indeed possess an endoblast and are thus distinct from the morphologically similar genera Pareodinia Deflandre and Kalyptea Cookson and Eisenack. The acritarch genus Pterospermella Eisenack, erected to accommodate species that were formerly included in Pterospermopsis W. Wetzel, is shown to be nomenclaturally superfluous; Baltisphaeridium pilosum var. lon‐gispinosum Sarjeant is rejected as a junior synonym of Prolixosphaeridium granulosum Deflandre. New illustrations of most of the species and forms discussed are presented.