From Fensome et al., 2019:
Microdinium glabrum Cookson and Eisenack, 1974, p.53, pl.20, fig.19. Holotype: Cookson and Eisenack, 1971, pl.7, fig.11, as Microdinium sp. Originally (and now) Microdinium, subsequently Phanerodinium. Lentin and Williams (1989, p.244) retained this species in Microdinium. Below (1987b, p.38) considered Microdinium (as Phaneordinium) distinctum to be the questionable taxonomic senior synonym of this species. Age: Senonian.

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Original diagnosis: Cookson and Eisenack, 1959, p. 53
A Microdinium-species with smooth plates and low, smooth lists.

Remarks: Cookson and Eisenack, 1959, p. 53
All remaining, up to now described species of the genus M. , in part, display ornamented plates and always denticulated, spine-bearing or perforated lists. Dimensions: Type-specimen about 33 µm long, 33 µm broad. The specimen illustrated here measures about 42 x 42 µm.

Occurrence: Madura No. 1 bore, at 1070-1104 ft.