From Fensome et al., 2019:
Spongodinium ?extremum (Cookson and Eisenack, 1974, p.48, pl.20, fig.4) Lentin and Williams, 1976, p.40. Holotype: Cookson and Eisenack, 1974, pl.20, fig.4. Originally Deflandrea, subsequently (and now) Spongodinium?, thirdly Isabelidinium?. Questionable assignment: Lentin and Williams (1976, p.40). Williams et al. (2017, p.774) retained this species questionably in Spongodinium. Age: Albian–Cenomanian.

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Original diagnosis: Cookson and Eisenack, 1974, p. 48: Deflandrea extrema
A species of the genus Deflandrea with a relatively thick wall, an in apical view circular endophragm and a thin-walled closely appressed periphragm. The short, pointed apical horn has a widened base, the two antapical horns are wide and blunt; all three are just weakly developed. The periphragm is folded with an irregular, small-meshed surface. Girdle not visible in apical view. Archaeopyle trapezoidal.
Dimensions: Endophragm ca. 85x85 µm, overall ca. 98x94 µm.