The late Jurassic dinoflagellate cyst Gonyaulacysta Ceratophora (Cookson & Eisenack 1960) comb.nov.,emend.nov.

The Late Jurassic (early Oxfordian to earliest Tithonian) dinoflagellate cyst Scriniodinium ceratophorum Cookson & Eisenack 1960 from Australia was originally described as having smooth walls and lacking tabulation except for the archeopyle and the cingulum. The type is an atypical end member of this distinctive species; most forms have partially developed tabulation. The species is closely related to Gonyaulacysta jurassica (Deflandre 1939) Norris & Sarjeant 1965. It has a relatively large epicyst, an apparently similar tabulation pattern to Gonyaulacysta jurassica and exhibits neutral torsion. Scriniodinium ceratophorum is therefore transferred to Gonyaulacysta and emended to include partially tabulate forms.