From Fensome et al., 2019:
Diconodinium glabrum Eisenack and Cookson, 1960, p.3–4, pl.1, fig.11. Holotype: Eisenack and Cookson, 1960, pl.1, fig.11;
Morgan, 1977, pl.2, figs.4a–c. Originally Diconodinium, subsequently (and now) Diconodinium?. Questionable
assignment: Morgan (1977, p.129). Age: late Albian–Cenomanian.

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Original description: Eisenack and Cookson, 1960, p. 4
Shell fusiform, epitheca usually longer than hypotheca, girdle prominent, "longitudinal furrow" strongly or weaklt outlined; apical process prominent, usually slightly bifid, antapical process well developed and sharpely pointed. Shell-membrane smoth inoptical section, surface either completely smooth or sparsely dotted with tiny granules.
Dimensions. Type 120 µm long, 70 µm broad. Range 62-142 µm long, 41-72 µm broad.

Supplemental description: Hultberg, 1985, p.
Proximate cyst, composed of autophragm only. The surface of the autophragm is smooth. The shape of the autophragm is biconical, with one single apical, and one single antapical horn. Both horns are sharply pointed. No indication of paratabulation is present, except archeopyle. The archeopyle is intercalary, type I, formed by the detachment of paraplate 2a. Operculum is often attached.
Paracingulum and parasulcus are clearly indicated by folds in the periphragm.
Size - 43-60 µm (length), 18-36 µm (breadth).