From Fensome et al., 2019:
Spinidinium rugosum (Stanley, 1965, p.222–223, pl.21, figs.6–11) Costa and Downie, 1979, p.45. Holotype: Stanley, 1965, pl.21, figs.10–11. Originally Wetzeliella, subsequently Wilsonidium?, thirdly Wetzeliella?, fourthly (and now) Spinidinium. Williams et al. (2015, p.318) retained this species in Spinidinium. Age: Paleocene.

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Locus typicus: South Dakota, USA
Stratum typicum: Paleocene

Original description: Stanley, 1965, p.222-223: Wetzeliella rugosa
Outer cyst rhomboidal to subrhomboidal in outline with the length being either slightly longer or slightly shorter than the width. Length varies between 50-60 µm whereas the width also varies between 50-60 µm. Outer cyst membrane thin and almost always irregularly folded or crumpled; membrane bears spinelike sculpture elements that have a length of about 1.5 to 2 µm. Apical horn about 3-5 µm in length; antapical horns two in number; the left one being well developed with a length of about 5 µm whereas the right one is poorly developed. Girdle indistinct but does appear to be bordered on both edges by a row of spinelike processes. Interior cyst thin-walled and more or less completely fills the outer cyst.

Affinities:
Stanley, 1965, p.223: Wetzeliella rugosa
Wetzeliella rugosa is differentiated from W. pilata, by ist spinlike sculture elements that lach any expansion at their distal ends.