From Fensome et al., 2019:
Apectodinium pastielsii, Lentin and Williams, 1989, p.18.
Holotype: Pastiels, 1948, pl.4, fig.4.
Name illegitimate — nomenclatural senior synonym: Baltisphaeridium (now Apectodinium) geometricum Pastiels, 1948 ex Downie and Sarjeant, 1965, which has the same holotype. This was proposed as a substitute name for Hystrichosphaeridium geometricum Pastiels, 1948, p.41, pl.4, figs.1–11.
Originally Hystrichosphaeridium geometricum (name illegitimate), subsequently Baltisphaeridium geometricum (Appendix A), thirdly Apectodinium pastielsii (name illegitimate), fourthly Apectodinium geometricum. According to Lentin and Williams (1989, p.18): "When Deflandre and Cookson (1955) created the species Wetzeliella homomorpha they placed Hystrichosphaeridium geometricum Pastiels in the synonomy and referred to 'Pastiels, 1945 pars.' but did not expressly include the holotype (Pastiels, 1948, pl.4, fig.4). By selecting a holotype for Wetzeliella homomorpha from their own material they created a new species, not a new name, as was assumed in previous issues of this index." Hence, Lentin and Williams (1989, p.18) proposed Apectodinium pastielsii as a new name. However, Fensome et al. (1990, p.617) noted that "... Hystrichosphaeridium geometricum Pastiels, is an illegitimate junior homonym of Hystrichosphaeridium geometricum Deflandre, 1945[a]. By 'transferring' Pastiels' species to Baltisphaeridium, Downie and Sarjeant (1965, [p.40]) created the valid and legitimate name Baltisphaeridium geometricum Pastiels ex Downie and Sarjeant. The name Apectodinium pastielsii is thus superfluous."

Age: Eocene.

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