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Palaeoperidinium ariadnae

From Fensome et al., 2019:
Palaeoperidinium ?ariadnae Norris, 1986, p.45, pl.12, figs.10–12; pl.13, figs.1–4. Holotype: Norris, 1986, pl.13, fig.2. Questionable assignment: Evitt et al. (1998, p.48). Age: Eocene.

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Locus typicus: Mackenzie Delta Regin, District of Mackenzie, Canada
Stratum typicum: Eocene

Original diagnosis: Norris, 1986, p. 45
Cysts proximate, slightly cornucavate, peridinioal outline, commonly broader than long. Antapical horns of unequal length, separated by a broad concavity. Periphragm scabrate, with sutural ridges along cingulum. Transapical sutures define archeopyle type (Atl3P). Logogram Pc; ap 2aa; (AIP); sut; pcin; per.

Original description: Norris, 1986, p. 45
The pericoels are 5-8 µm long and are discernible only with difficulty in most specimens. Cingulum helicoid, approximately 5 µm wide, delimited by low ridges, divides cyst into larger epicyst and smaller hypocyst. Narrow quasi-tabular ridges radiate out below the apex and are approximately 5 µm in length.

Dimensions: Length 44-63 µm; width 45-65 µm. Holotype. 44 µm x 45 µm.

Affinities:
Norris, 1986, p. 45: Distinguished from other species of Palaeoperidinium by its relatively small size, relatively wider dimensions, broadly separated antapical horns, and small hypocyst.
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