Baltisphaeridium pumile, (O. Wetzel, 1932 ex O. Wetzel, 1933), Downie and Sarjeant, 1963

Name illegitimate; nomenclatural jr. synonym of Hystrichosphaera (now Baltisphaeridium) lingispinosa forma longispinosa, the potential autonym since, in validating Hystrichosphaera longispinosa forma pumilis, O. Wetzel, 1933 included in synonymy the holotype of the species. Also combination not validly published since Downie and Sarjeant, 1963 did not fully reference the basionym. See also Hystrichosphaera longispinosa forma pumilis (name illegitimate), Hystrichosphaeridium pumile (name illegitimate), Micrhystridium pumile (an acritarch species; name illegitimate), and Diacrocanthidium? pumile (name illegitimate). The name Hystrichosphaera longispinosa forma pumilis, although accompanied by a description, was not validly published by O. Wetzel, 1932 since the generic name Hystrichosphaera was not validly published until 1933. In validly publishing, but not legitimizing, the name Hystrichosphaera longispinosa forma pumilis, O. Wetzel, 1933 illustrated only one specimen but listed in synonymy several more, including the holotype of the species; he did not designate any of these specimens as holotype. Based on reexamination of the single specimen illustrated by O. Wetzel, 1933, which he indicated as holotype, Sarjeant, 1985 questionably included this species in Diacrocanthidium.

Holotype: O. Wetzel, 1933, pl.4, fig.24; designated by Sarjeant, 1985
Age: Late Cretaceous (based on material from an erratic)