From Fensome et al., 2019:
Tenua microcysta Bujak in Bujak et al., 1980, p.88,90, pl.22, figs.2–5.
Holotype: Bujak et al., 1980, pl.22, figs.2–3; Fauconnier and Masure, 2004, pl.64, figs.4–5.
NOW Sentusidinium. Originally Tenua Eisenack, subsequently Cleistosphaeridium, thirdly (and now) Sentusidinium, fourthly Pilosidinium.
Age: Middle Eocene (see Aubry, 1986).
Paratype: Bujak in Bujak et al. 1980
Locus typicus: Alum Bay, Isle of Wight, southern England
Stratum typicum: Late Eocene

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Original diagnosis: Bujak in Bujak et al., 1980, p.88-89
Autocyst ovoidal, sometimes with two weakly developed antapical lobes. Autophragm smooth to chagrinate with abundant processes. The processes are nontabular and are of constant length on a specimen, but vary in length intraspecifically. The processes are mostly expanded proximally, hollow, and are distally capitate or bifid. Occasional processes are solid or simple. The archaeopyle is apical, tetratabular, and has well-developed accessory archaeopyle sutures between the precingular paraplates. The operculum is detached.
Dimensions. Autocyst length (without operculum) = 28-36 µm, breadth = 24-34 µm. Process length is up to 6 µm.