Acanthodiacrodium hamatum, (Downie, 1958), Martin, 1973

Now Baltisphaeridium hamatum. Originally Hystrichosphaeridium hirsutoides var. hamatum, subsequently Baltisphaeridium hirsutoides var. hamatum, thirdly Micrhystridium hamatum, fourthly Acanthodiacrodium hamatum, fifthly (and now) Baltisphaeridium hamatum.
This taxon was raised to specific rank by Deflandre and Deflandre-Rigaud, 1965 as Micrhystridium hamatum.

Holotype: Downie, 1958, pl.16, fig.1
Age: Early Ordovician