Palaeoperidinium larjakiense (Vozzhennikova, 1967) Lentin and Williams, 1981

Originally Peridinium conicum var. Iarjakiense, subsequently Palaeoperidinium deflandrei ssp. Iarjakiense, thirdly Cooksoniella larjakiensis, fourthly Palaeoperidinium larjakiense.
Taxonomic senior synonym: Peridinium (now Palaeoperidinium) pyrophorum, according to Lentin and Vozzhennikova (1990, p.61).

Holotype: Vozzhennikova, 1967, pl.16, figs.1a-b; Lentin and Vozzhennikova, 1990, text-fig.32 (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.71-72: Peridinium conicum var. larjakiense
Armour broadly pentagonal, dorso-ventrally compressed, with a small apical outgrowth (horn) and with short slightly tapering and widely separated antapical horns. Transverse furrow equatorial, its margin bounded by small processes. Position of longitudinal furrow indistinct. The armour plates are broad fields, the sculpture of which consists of alternating transverse and longitudinal striations. The surface of the armour is finely dotted or finely punctuate. On the dorsal side there is a small round or trapeziform pylome formed as a result of the loss of the third intermediate plate.
Size: Holotype, length 148.5 µm, breadth 124 µm, width of transverse furrow 8 µm. lsolated specimen.