Xanthidium spinosum White, 1842

Now Exochosphaeridium?. Originally Xanthidium, subsequently Hystrichosphaeridium, thirdly Baltisphaeridium (an acritarch genus), fourthly Exochosphaeridium, fifthly (and now) Exochosphaeridiuim?; see also Cordosphaeridium (combination not validly published).

Holotype: White, 1842, pl.4, fig.6
Age: Late Cretaceous