From Fensome et al., 2019:
Yolkinigymnium lanceolatum (May, 1977, p.115, pl.2, figs.9–10) Lentin and Vozzhennikova, 1990, p.30. Holotype: May, 1977, pl.2, figs.9–10; Lentin and Vozzhennikova, 1990, Appendix A, fig.41.

Originally Dinogymnium, subsequently (and now) Yolkinigymnium.

Holotype: May, 1977, pl.2, figs.9-10; Lentin and Vozzhennikova, 1990, Appendix A, fig.41
Local stratigraphic range: Late Campanian-Early Maastrichtian
Type locality: Atlantic Highlands, New Jersey
Type stratum: Mount Laurel Sand.

Original description: May, 1977 (as Dinogymnium lanceolatum):
Description: Delicate, elongate test, ca. 8-12 times longer than wide; appears single layered. Epitract lanceolate, tapering to a pointy length is 1/4 to 1/5 of total cyst, separated from hypotract by shallow, weakly-defined, levorotatory cingulum having offset ca. 1/2 cingulum width. Epitract nearly as broad as hypotract across cingulum. Hypotract tapers to a rounded antapex.
No archeopyle observed.
Surface finely scabrate.

Dimensions:
Holotype 140 µm x 13 µm. Observed range (four specimens measured): length 140-165 µm, width 13-20 µm. Cyst wall ca. 0.5 µm thick. Cingulum index range 21-26.

Affinity: Same as D. elongatum. Dinogymnium lanceolatum compares with certain modern Gymnodinium speices in the same manner as reprted for D. elongatum. The long delicate hypotract tends to fold and collapse.

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Lentin and Vozzhennikova, 1990: