Pentagonum marginatum Vozzhennikova, 1967

Originally Pentagonum (an illegitimate generic name), subsequently Palaeoperidinium.
Taxonomic senior synonym: Peridinium (now Palaeoperidinium) pyrophorum, according to Lentin and Vozzhennikova (1990, p.61).
Following I.C.N. Article 55.1, the species name Pentagonum marginatum is validly published even though the generic name Pentagonum is illegitimate.

Holotype: Vozzhennikova, 1967, pl.46, fig.6; Lentin and Vozzhennikova, 1990, p.7, fig.6, text-fig. 33; (lost according to Lentin and Vozzhennikova, 1990)
Lectotype: none available according to Lentin and Vozzhennikova, 1990
Locus typicus: Western Siberia, USSR
Stratum typicum: Palaeocene
Translation Vozzhennikova, 1967: Lentin and Vozzhennikova, 1990

Original description: Vozzhennikova, 1967, p.107
Theca strongly compressed in a torso- ventral direction; epitheca slightly larger than hypotheca, triangular in outline with straight or slightly curved sites ant with a short, blunt-ended apical horn. Hypotheca trapeziform with 2 short, widely separated antapical horns. Transverse furrow equatorial, annual, its borders having a narrow rim. Longitudinal furrow extends over the hypotheca and apparently reaches the antapex. One, or less frequently two, sides of the theca have a borter striated with transverse parallel lines. The borter increases in width towards the transverse furrow. Theca thin walled, smooth, or f inely punctuate, pale yellow in color.
Size: Holotype, length 124 Ám, width 99 Ám, width of transverse furrow about 6 or 7 Ám. Range, length 120-127 Ám, width 92-99 Ám.