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Microdinium distinctum

From Fensome et al., 2019:
Microdinium distinctum Davey, 1969a, p.133–135, pl.2, figs.9–11; text-figs.13D–E,I. Holotype: Davey, 1969a, pl.2, figs.9–10; text-fig.13D. Originally (and now) Microdinium, subsequently Phanerodinium. Lentin and Williams (1989, p.244) retained this species in Microdinium. Below (1987b, p.38) considered Microdinium? (as Phanerodinium) variospinum, Microdinium glabrum and Microdinium (as Phanerodinium) opacum to be questionable taxonomic junior synonyms of this species. Age: early Cenomanian.

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Locus typicus: Fetcham Mill, England
Stratum typicum: Early Cenomanian

Original diagnosis: Davey, 1969, p. 133
Shell subspherical, thick-walled, smooth. Sutural crests well developed bearing short, broad, flat-topped spines. Reflected tabulation I, oa, 6'' 6''', 1p, 1''''; plates 1" and 6" very reduced and cingular plates absent. Cingulum broad, weakly laevo-rotatory.

Original description: Davey, 1969, p. 133-134
The shell wall is relatively thick, c. 1 µm, and develops pronounced ridges at the plate boundaries. The sutural spines are closely set, very broad and flat distally.
The precingular plates are generally smaller than the postcingular plates. Plates 1" and 6" are small and appear as slight projections in the ventral area. This is widest posteriorly and is open anteriorly. The apical plate is six-sided and is lost in archaeopyle formation. The archaeopyle possesses slits extending posteriorly between the precingular plates.
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