From Fensome et al., 2019:
Batiacasphaera explanata (Bujak in Bujak et al., 1980, p.44, pl.13, figs.13–14) Wood et al., 2016, p.84. Holotype: Bujak et al., 1980, pl.13, figs.13–14. Originally Chytroeisphaeridia, subsequently Batiacasphaera, thirdly (and now)
Sentusidinium. Taxonomic junior synonyms: Canningia minor var psilata, Escharisphaeridia laevigata,
Kallosphaeridium inornatum, and Kallosphaeridium praussii, all according to Wood et al. (2016, p. 84–85);
Escharisphaeridia nuda, by implication — Prauss (in Lentin and Williams, 1993, p.213) and Feist-Burkhardt and
Monteil (1998, p.40) considered Escharisphaeridia nuda to be a taxonomic junior synonym of Escharisphaeridia
laevigata, which is now considered a taxonomic junior synonym of Sentusidinium explanatum. Wood et al. (2016,
p.85) noted that, although Canningia minor var. psilata is the earliest name for this taxon, "explanatum" is the
earliest epithet at specific rank. Age: Middle Eocene (see Aubry, 1986) .

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Original description as Chytroeisphaeridia explanata: [Bujak in Bujak et al., 1980]:

Diagnosis:
Autocyst spherical to ovoidal. Autophragm smooth to chagrinate, without indication of paracingulum or parasulcus.
Paratabulation absent except near the archaeopyle margin.
Archaeopyle apical, tetratabular, with well-developed accessory archaeopyle sutures that delimit the lateral margins of paraplates 1"-6" and a.s. The operculum is detached.

Dimensions:
Autocyst length (without operculum) = 44-66 µm, breadth = 48-70 µm.