From Fensome et al., 2019:
Diconodinium ventriosum (Alberti, 1961, p.5–6, pl.3, fig.5) Lentin and Williams, 1973, p.47. Holotype: Alberti, 1961, pl.3, fig.5. Originally Gymnodinium (Appendix B), subsequently (and now) Diconodinium. Morgan (1977, p.130) stated that Gymnodinium ventriosum was transferred to Subtilisphaera Jain and Millepied, 1973, by Jain and Millepied (1973, p.27); however, we have been unable to verify this. Age: Turonian.

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Original description: [Alberti, 1961] (translated from German):

Gymnodinium ventriosum n. sp.
Plate 3 Fig. 5

Holotype: The specimen preserved in specimen No. A 2 and shown in Plate 3 Fig. 5.
Typical location: Opole (Silesia).
Typical stratum: Turonian.
Diagnosis: Body lemon-shaped, dorsoventrally flattened, epidermal and hypodermal lobes almost equal in size.
Sometimes a small, often somewhat pointed lobe at each pole. The transverse furrow is narrow, slightly depressed, and, like the longitudinal furrow, indistinct. The body surface is rough.
Notes: The outline of the body is often somewhat asymmetrical. The delicate membrane causes a fine wrinkling of the entire surface.
Dimensions of the holotype: Length 95 μ, width 80 μ. For other specimens, the length varies between 85 and 95 μ, and the width between 68 μ and 80 μ.
Material: Over 20 specimens.
Occurrence: Hauterive — Alb of Haverlahwiese, Turon of Oppeln.