From Fensome et al., 2019:
Impletosphaeridium ?polytrichum (Valensi, 1947, p.818; text-fig.4) Islam, 1993, p.87. Holotype: Valensi, 1947; text-fig.4; Fauconnier
and Masure, 2004, pl.24, figs.1–6. Originally Hystrichosphaeridium, subsequently Baltisphaeridium (Appendix A), thirdly Cleistosphaeridium, fourthly Impletosphaeridium, fifthly Downiesphaeridium, sixthly (and now) Impletosphaeridium?. Questionable assignment: Peyrot (2011, p.293–294). Taxonomic junior synonym: Cleistosphaeridium (as Downiesphaeridium) polyacanthum, according to Masure in Fauconnier and Masure (2004, p.196). Age: late Bathonian.

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