Micrhystridium longispinosum (Eisenack, 1931 ex O. Wetzel, 1933) Cramer et al., 1979

Combination not validly published since Cramer et al., 1979 did not reference the basionym.
Now Baltisphaeridium longispinosum (an acritarch species). Originally
Hystrichosphaera longispinosa, subsequently Hystrichosphaeridium longispinosum, thirdly (and now) Baltisphaeridium longispinosum (an acritarch species), fourthly Micrhystridium longispinosum (name not validly published); see also Ovum hispidum ssp. Iongispinosum (name not validly published). According to Fensome et al., 1990: Apparently, Cramer et al., 1979 did not intend to propose this combination, only to "transfer" two infraspecific taxa ["M. Iongispinosum br (Downie, 1963) Cramer et al. (herein)" ... and "M. Iongispinosum parvum (Downie, 1963) Cramer n. comb. (herein)"] to Micrhystridium. If this species were to be
transferred to Micrhystridium, If it is the type of Baltisphaeridium Eisenack, 1958, the latter genus would become a jr. synonym of Micrhystridium. The name Ovum hispidum ssp. longispinosum was not validly published in Eisenack, 1931 since the specific name Ovum hispidum is not validly published."
Holotype: Eisenack, 1931, pl.5, fig.10; lost, according to Eisenack, 1959
Neotype: Eisenack, 1959, pl.15, fig.1; designated by Eisenack, 1959
Age: Ordovician (Early Caradoc)