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Isabelidinium cretaceum ssp. gravidum
Isabelidinium cretaceum ssp. gravidum Mao Shaozhi and Mohr, 1992
Now Manumiella? cretacea ssp. gravida. Originally Isabelidinium cretaceum ssp. gravidum, subsequently (and now) Manumiella? cretacea ssp. gravida.
Holotype: Mao Shaozhi and Mohr, 1992, pl.1, fig.11
Locus typicus: ODP Hole 748c, Banzare Bank, S Indian Ocean
Stratum typicum: Maastrichtian
Original description: Mao Shaozhi and Mohr, 1992, p. 319
Cyst bicavate. Both apex and antapex rounded without horns. Endocyst spherical to transversely elliptical, forming the widest part and occupying the major portion of the cyst. Cyst asymmetrical to both long and short axes or only to long axis with the apical pericoel larger than the antapical pericoel. Wall thin and two layered; both periphragm and endophragm smooth. Archeopyle intercalary [2a], standard hexastyle, iso-thetaform or rounded at each corner; AI = 0.52-0.65; operculum free.
Size. Length of cysts, 73.5-99.5 (holotype 90) µm; width of cysts, 58.5-80.5 (holotype 80) µm; length of cysts/width of cysts= 1.1-1.6; 20 specimens measured.
Affinities: Mao Shaozhi and Mohr, 1992, p. 319
The present subspecies is characterized by its bicavate cyst and transversely expanded endocyst. The present new subspecies is similar to some specimens of Isabelidinium greenense Marshall,1990 (figs. 21-D and 21-E only). According to the description (Marshall, 1990, p. 24), "ventro-dorsal outline of endocyst subcircular to ovoidal and longitudinally elongate." Figures 21-Dand 21-E, however, show the endocyst to be transversely elliptical rather than longitudinally elongate in outline, which is similar to the present new subspecies. We, therefore, consider them to be conspecies and consubspecies with the present subspecies. The subspecies differs from 1. cretaceum cretaceum by having a rounded antapex, whereas the latter subspecies has a concave antapex and includes forms of both bicavate cysts and circumcavate cysts with very narrow lateral pericoel.
Now Manumiella? cretacea ssp. gravida. Originally Isabelidinium cretaceum ssp. gravidum, subsequently (and now) Manumiella? cretacea ssp. gravida.
Holotype: Mao Shaozhi and Mohr, 1992, pl.1, fig.11
Locus typicus: ODP Hole 748c, Banzare Bank, S Indian Ocean
Stratum typicum: Maastrichtian
Original description: Mao Shaozhi and Mohr, 1992, p. 319
Cyst bicavate. Both apex and antapex rounded without horns. Endocyst spherical to transversely elliptical, forming the widest part and occupying the major portion of the cyst. Cyst asymmetrical to both long and short axes or only to long axis with the apical pericoel larger than the antapical pericoel. Wall thin and two layered; both periphragm and endophragm smooth. Archeopyle intercalary [2a], standard hexastyle, iso-thetaform or rounded at each corner; AI = 0.52-0.65; operculum free.
Size. Length of cysts, 73.5-99.5 (holotype 90) µm; width of cysts, 58.5-80.5 (holotype 80) µm; length of cysts/width of cysts= 1.1-1.6; 20 specimens measured.
Affinities: Mao Shaozhi and Mohr, 1992, p. 319
The present subspecies is characterized by its bicavate cyst and transversely expanded endocyst. The present new subspecies is similar to some specimens of Isabelidinium greenense Marshall,1990 (figs. 21-D and 21-E only). According to the description (Marshall, 1990, p. 24), "ventro-dorsal outline of endocyst subcircular to ovoidal and longitudinally elongate." Figures 21-Dand 21-E, however, show the endocyst to be transversely elliptical rather than longitudinally elongate in outline, which is similar to the present new subspecies. We, therefore, consider them to be conspecies and consubspecies with the present subspecies. The subspecies differs from 1. cretaceum cretaceum by having a rounded antapex, whereas the latter subspecies has a concave antapex and includes forms of both bicavate cysts and circumcavate cysts with very narrow lateral pericoel.