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Millioudodinium venulosum
Millioudodinium? venulosum Mao Shaozhi and Norris, 1988
Now Cribroperidinium?. Originally Millioudodinium?, subsequently (and now) Cribroperidinium?.
Mao Shaozhi and Norris, 1988, questionably included this species in Millioudodinium.
Holotype: Mao Shaozhi and Norris, 1988, pl.3, fig.1
Locus typicus: Wuluokeqiate section, China
Stratum typicum: Late Cretaceous
Original diagnosis: Mao Shaozhi and Norris, 1988, p. 34
Cyst proximate, typically of intermediate size, laterally flattened, ambitus elliptical to rounded rhombic. Apical horn usually short but distinct. Tabulation gonyaulacacean, indicated usually by indistinct low sutural ridges; possible formula of 4", ? 1a, 6", Xc, 6""", 1p, 1"""", if determinable; faint, incomplete, slightly sinuous, and very low ridges, giving autophragm a reticulate appearance. Archeopyle precingular type (P)a or P; operculum 3" attached along part of its two sides with 2" and 4".
Original description: Mao Shaozhi and Norris, 1988, p. 34
Cyst ambitus elliptic to subrhombic with short (typically 4 to 7 Ám high), prominent apical horn. Antapex rounded, without horns or prominences. Cingulum levorotatory, usually 3 to 4 Ám wide, defined by sutural ridges of low to medium height. Sutural ridges indistinct, obviously gonyaulacacean. Surface between sutural ridges covered with faint, discontinuous, slightly sinuous low ridges, giving autophragm a veinlike-reticulate appearance. Omphalos often found ventrally within cyst body near boundary where cingulum and sulcus meet.
Dimensions: Length 71 to 97 Ám (holotype 80 Ám), width 55 to 75 Ám (holotype 62 Ám).
Affinities:
Mao Shaozhi and Norris, 1988, p. 35: This species is characterized by having an elliptic to ebngate rhombic ambitus, usually laterally flattened; very low and indistinct sutural ridges, with which some details of tabulation are interpreted with difficulty; and an autophragm with a typically imperfect microreticulate appearance between the sutures. It is assigned questionably to Millioudodinium rather than to Cribroperidinium because of the lack of some detailed information on tabulation and the lack of accessory sutures. M. (?) venulosum resembles M. globatum (Gitmez and Sarjeant, 1972), which possesses a granulate autophragm and generally well developed sutures, indicating the tabulation formula of 4", 1a, 6", 6c, 6""", ?1p, and 1"""". M. (?) venulosum differs from M. (?) aequum in having distinctly elongate cysts; the latter has spherical to broad spherical cysts (see Text-Fig. 9).
Text-Figure 9 shows that there are almost no intermediate forms between the two species.
Now Cribroperidinium?. Originally Millioudodinium?, subsequently (and now) Cribroperidinium?.
Mao Shaozhi and Norris, 1988, questionably included this species in Millioudodinium.
Holotype: Mao Shaozhi and Norris, 1988, pl.3, fig.1
Locus typicus: Wuluokeqiate section, China
Stratum typicum: Late Cretaceous
Original diagnosis: Mao Shaozhi and Norris, 1988, p. 34
Cyst proximate, typically of intermediate size, laterally flattened, ambitus elliptical to rounded rhombic. Apical horn usually short but distinct. Tabulation gonyaulacacean, indicated usually by indistinct low sutural ridges; possible formula of 4", ? 1a, 6", Xc, 6""", 1p, 1"""", if determinable; faint, incomplete, slightly sinuous, and very low ridges, giving autophragm a reticulate appearance. Archeopyle precingular type (P)a or P; operculum 3" attached along part of its two sides with 2" and 4".
Original description: Mao Shaozhi and Norris, 1988, p. 34
Cyst ambitus elliptic to subrhombic with short (typically 4 to 7 Ám high), prominent apical horn. Antapex rounded, without horns or prominences. Cingulum levorotatory, usually 3 to 4 Ám wide, defined by sutural ridges of low to medium height. Sutural ridges indistinct, obviously gonyaulacacean. Surface between sutural ridges covered with faint, discontinuous, slightly sinuous low ridges, giving autophragm a veinlike-reticulate appearance. Omphalos often found ventrally within cyst body near boundary where cingulum and sulcus meet.
Dimensions: Length 71 to 97 Ám (holotype 80 Ám), width 55 to 75 Ám (holotype 62 Ám).
Affinities:
Mao Shaozhi and Norris, 1988, p. 35: This species is characterized by having an elliptic to ebngate rhombic ambitus, usually laterally flattened; very low and indistinct sutural ridges, with which some details of tabulation are interpreted with difficulty; and an autophragm with a typically imperfect microreticulate appearance between the sutures. It is assigned questionably to Millioudodinium rather than to Cribroperidinium because of the lack of some detailed information on tabulation and the lack of accessory sutures. M. (?) venulosum resembles M. globatum (Gitmez and Sarjeant, 1972), which possesses a granulate autophragm and generally well developed sutures, indicating the tabulation formula of 4", 1a, 6", 6c, 6""", ?1p, and 1"""". M. (?) venulosum differs from M. (?) aequum in having distinctly elongate cysts; the latter has spherical to broad spherical cysts (see Text-Fig. 9).
Text-Figure 9 shows that there are almost no intermediate forms between the two species.