Palaeoperidinium monacanthum

"monacanthum" Deflandre, 1936b, p.176–177, pl.5, fig.10.  Holotype: Deflandre, 1935, pl.6, fig.1; Deflandre, 1936b, pl.5, fig.10; lost according to Jan du Chêne et al. (1986a, p.48).  Name not validly published: generic name not validly published until 1967.  NOW Apteodinium?.  Originally Palaeoperidinium (name not validly published), subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly Apteodinium, fifthly (and now) Apteodinium?.  This name was not validly published in Deflandre (1935, p.227–228), since the genus Palaeoperidinium was not validly published until 1967 and, additionally, since that author did not provide a description.  Age: Senonian.

Parent: Palaeoperidinium