Arkellidinium triapertum

"*triapertum" Beju, 1979, p.4–5, fig.1, nos.1–6; figs.2A–A',B–E.  Holotype: Beju, 1979, fig.1, no.1; figs.2A–A'; Fensome et al., 1995, figs.1,7–8 — p.1847.  Originally Arkellidinium, subsequently Sirmiodiniopsis.  Taxonomic senior synonym: Sirmiodiniopsis orbis, according to Riley and Fenton (1982, p.199).  Age: late Callovian.

Parent: Arkellidinium