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Cribroperidinium aequum
From Fensome et al., 2019:
Cribroperidinium? aequum (Mao Shaozhi and Norris, 1988, p.35, pl.2, figs.17–19; text-fig.9) Lentin and Williams, 1989, p.79. Holotype: Mao Shaozhi and Norris, 1988, pl.2, fig.17. Originally Millioudodinium?, subsequently (and now) Cribroperidinium?. Questionable assignment: Lentin and Williams (1989, p.79). Age: Late Cretaceous.
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Original diagnosis: Mao Shaozhi and Norris, 1988, p.35: Millioudinium aequum
Cyst proximate, typically of intermediate size (50 Ám), spherical with a small prominent apical horn. Autophragm thin, readily folding along cyst margin.
Tabulation gonyaulacacean, indicated by low sutural ridges; faint, veinlike low ridges between sutural ridges masking some details of tabulation. Archeopyle precingular, type (P)a, formed by loss of 3"; operculum typically attached along part of sides with 2" and/or 4", sometimes indiscernible. Cingulum helicoid.
Original description: Mao Shaozhi and Norris, 1988, p. 35: Millioudinium aequum
Cyst spherical to broadly spherical. Apical horn small but pointed, commonly 2 to 5 Ám long. Antapex rounded, lacking horns or prominences. Specimens randomly oriented because of sphericity, folding readily because of thin wall. Cingulum levorotatory, usually 3 to 4 Ám wide, bounded by ridges less than 0.5 Ám high. Sulcus extending from cingulum towards antapex. Sutural ridges indistinct; possible tabulation formula of 4", ?la, 6", Xc, 6""", 1p, 1"""", if determinable. Surface between sutural ridges covered with incomplete, faint, slightly sinuous low ridges, giving the thin autophragm a veinlike reticulate appearance. Omphalos often darker in colour, spherical to subspherical in shape. Dimensions: Length 55 to 75 Ám (holotype 70 Ám), width 62 to 71 Ám (holotype 70 Ám).
Affinities:
Mao Shaozhi and Norris, 1988, p. 35: Millioudinium aequum
Millioudodinium (?) aequum closely resembles M. (?) venulosum but differs in having a spherical rather than an elongate cyst. Text-Figure 9 shows almost no intermediate forms between them. As with M. (?) venulosum, the generic assignation is questionable to Millioudodinium rather than Cribroperidinium because of the imperfect microreticulate low ridges (which are not certainly accessory ridges typical of Cribroperidinium) and the lack of detailed information on tabulation.
Cribroperidinium? aequum (Mao Shaozhi and Norris, 1988, p.35, pl.2, figs.17–19; text-fig.9) Lentin and Williams, 1989, p.79. Holotype: Mao Shaozhi and Norris, 1988, pl.2, fig.17. Originally Millioudodinium?, subsequently (and now) Cribroperidinium?. Questionable assignment: Lentin and Williams (1989, p.79). Age: Late Cretaceous.
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Original diagnosis: Mao Shaozhi and Norris, 1988, p.35: Millioudinium aequum
Cyst proximate, typically of intermediate size (50 Ám), spherical with a small prominent apical horn. Autophragm thin, readily folding along cyst margin.
Tabulation gonyaulacacean, indicated by low sutural ridges; faint, veinlike low ridges between sutural ridges masking some details of tabulation. Archeopyle precingular, type (P)a, formed by loss of 3"; operculum typically attached along part of sides with 2" and/or 4", sometimes indiscernible. Cingulum helicoid.
Original description: Mao Shaozhi and Norris, 1988, p. 35: Millioudinium aequum
Cyst spherical to broadly spherical. Apical horn small but pointed, commonly 2 to 5 Ám long. Antapex rounded, lacking horns or prominences. Specimens randomly oriented because of sphericity, folding readily because of thin wall. Cingulum levorotatory, usually 3 to 4 Ám wide, bounded by ridges less than 0.5 Ám high. Sulcus extending from cingulum towards antapex. Sutural ridges indistinct; possible tabulation formula of 4", ?la, 6", Xc, 6""", 1p, 1"""", if determinable. Surface between sutural ridges covered with incomplete, faint, slightly sinuous low ridges, giving the thin autophragm a veinlike reticulate appearance. Omphalos often darker in colour, spherical to subspherical in shape. Dimensions: Length 55 to 75 Ám (holotype 70 Ám), width 62 to 71 Ám (holotype 70 Ám).
Affinities:
Mao Shaozhi and Norris, 1988, p. 35: Millioudinium aequum
Millioudodinium (?) aequum closely resembles M. (?) venulosum but differs in having a spherical rather than an elongate cyst. Text-Figure 9 shows almost no intermediate forms between them. As with M. (?) venulosum, the generic assignation is questionable to Millioudodinium rather than Cribroperidinium because of the imperfect microreticulate low ridges (which are not certainly accessory ridges typical of Cribroperidinium) and the lack of detailed information on tabulation.