Hystrichosphaera xanthiopyxides Wetzel, 1933b, p.44–45, pl.4, fig.25. Emendations: Morgenroth, 1968, p.556, as Hystrichosphaeridium? xanthiopyxides; Sarjeant, 1985b, p.142–144, as Tanyosphaeridium xanthiopyxides.

Name not validly published: generic name not validly published until 1937.
NOW Tanyosphaeridium. Originally Hystrichosphaera (name not validly published), subsequently Hystrichosphaeridium, thirdly Hystrichosphaeridium?, fourthly Baltisphaeridium (Acritarch), fifthly Prolixosphaeridium?, sixthly (and now) Tanyosphaeridium.
Taxonomic junior synonym: Hystrichosphaeridium (as Tanyosphaeridium) magdalium, according to Stover and Evitt (1978, p.85).

Holotype: Wetzel, 1933b, pl.4, fig.25, Morgenroth, 1968, pl.48, fig.5; Sarjeant, 1985b, pl.3, figs.2–3; Dietz et al., 1999, fig.10, no.8.
Age: Late Cretaceous (?Maastrichtian, according to Sarjeant, 1985b, p.143).