From Fensome et al., 2019:
Rhynchodiniopsis cladophora ssp. extensa (Klement, 1960, p.36–37, pl.4, figs.1–4; text-fig.16) Below, 1981a, p.118. Holotype: Klement, 1960, pl.4, figs.1–3; Jan du Chêne et al., 1986a, pl.95, figs.4–5. Originally Gonyaulax cladophora subsp. extensa (Appendix B), subsequently Gonyaulacysta cladophora subsp. extensa, thirdly Hystrichogonyaulax cladophora subsp. extensa, fourthly (and now) Rhynchodiniopsis cladophora subsp. extensa. Taxonomic senior synonym: Gonyaulax (as Rhynchodiniopsis) cladophora subsp. cladophora, by implication in Brenner (1988, p.72), who listed this subspecies as a taxonomic junior synonym of the species Rhynchodiniopsis cladophora — however, Lentin and Williams (1993, p.566) retained Gonyaulax (as Rhynchodiniopsis) cladophora subsp. extensa. Age: early Kimmeridgian.

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