Hystrichosphaeridium hirsutum (Ehrenberg, 1837b, pl.1, figs.10,?13) Deflandre, 1939a, p.78.

Name not validly published: Ehrenberg (1837b) did not intend to introduce a new species.
Originally Xanthidium hirsutum (name not validly published; acritarch), subsequently Ovum hispidum subsp. hirsutum (name not validly published; acritarch), thirdly Hystrichosphaera hirsuta (name not validly published), fourthly Hystrichosphaeridium hirsutum (name not validly published), fifthly Baltisphaeridium hirsutum (name not validly published; acritarch), sixthly Operculodinium hirsutum (name not validly published), seventhly Operculodinium? hirsutum (name not validly published). See discussion under Operculodinium? hirsutum.

Age: Late Cretaceous.