From Williams et al., 2017:

[Pachysphaeridium, Burmann, 1970, p. 310–311.
Acritarch genus.

Type species: as Baltisphaeridium longispinosum, Eisenack, 1959 (pl.15, fig.2) (now accommodated in Pachsphaeridium robustum — see Fensome et al., 1990, p.383).]