Downiesphaeridium polytrichum (Valensi, 1947, p.818; text-fig.4) Masure in Fauconnier and Masure, 2004, p.196.

NOW Impletosphaeridium? Originally Hystrichosphaeridium, subsequently Baltisphaeridium (acritarch), thirdly Cleistosphaeridium, fourthly Impletosphaeridium, fifthly Downiesphaeridium, sixthly (and now) Impletosphaeridium?.
Taxonomic junior synonym: Cleistosphaeridium (as Downiesphaeridium) polyacanthum, according to Masure in Fauconnier and Masure (2004, p.196).

Holotype: Valensi, 1947, text-fig.4; Fauconnier and Masure, 2004, pl.24, figs.1-6.
Age: Late Bathonian.