Baltisphaeridium heteracanthum, (Deflandre and Cookson, 1955), Downie and Sarjeant, 1965

Now Heterosphaeridium?. Originally Hystrichosphaeridium, subsequently Baltisphaeridium, thirdly Cleistosphaeridium fourthly Heterosphaeridium, fifthly (and now) Heterosphaeridium?. This combination was not validly published in
Downie and Sarjeant, 1963 since these authors did not fully reference the basionym.

Holotype: Deflandre and Cookson, 1955, pl.2, fig.5
Age: ?Late Cretaceous-early Eocene