Visbysphaera pirifera (Eisenack, 1954) Kiryanov, 1978

Originally Hystrichosphaeridium, subsequently Baltisphaeridium (an acritarch genus), thirdly Multiplicisphaeridium (an acritarch genus), fourthly (and now) Visbysphaera.
Tax. sr. synonym of the acritarch species Baltisphaeridium hermosum Cramer and Diez, 1968 (an invalid name), according to Cramer, 1970. This combination was not validly published in Lister, 1970 since that author did not clearly use the name Visbysphaera pirifera. This combination is not attributable to Le Herisse, 1984. Although Eisenack, 1965 considered the species to be the tax. sr. synonym of
the acritarch species Baltisphaeridium (now Visbysphaera) dilatispinosum Downie, 1963, the type species of Visbysphaera, Eisenack et al., 1973 more cautiously stated that Baltisphaeridium (as Multiplicisphaeridium) dilatispinosum is "probably a practical jr. synonym of Multiplicisphaeridium piriferum". Because of this degree of doubt regarding the synonymy of these two species, Fensome et al., 1990 retained Visbysphaera dilatispinosa as a separate species.
Holotype: Eisenack, 1954, pl.1, figs.1a-b
Age: Silurian (Late Llandovery)