|Citation: Helgolandinioideae Fensome et al. 1993b.|
Diagnosis:Goniodomaceans with either or both of the following characters: 1) the tabulation has more than the typical goniodominean number of plates in at least two plate series; 2) within the life-cycle there is a nonpreservable smooth cellulosic cyst with a chasmic archeopyle.
Helgolandinium von Stosch 1969.
Alexandrium Halim 1960a.