Genus Gonyaulax Diesing, 1866
Cells armoured. Cells subspherical to biconical to fusiform with a descending cingulum, with or without cingulum overhang. 1' plate can be sigmoid and narrow to rhomboidal. Some species with apical horns and posterior spines. Theca varies in thickness and surface markings. APC with oval pore plate or elongate oval pore plate, often with linear markings. Plate formula: Po, 3', 2a, 6'', 6c, 7s, 6''', 2''''. Chloroplasts present. Benthic cysts.
Some bloom-forming red tide species.
Remarks: Species of this genus are differentiated based on the following characteristics: 1) size and shape; 2) plate tabulation and pattern; 3) APC; 4) cingulum displacement and overhang; 5) development of apical process/horn; and 6) ornamentation.
Species included from this genus:
Gonyaulax polygramma Stein, 1883