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Impagidinium fenestroseptatum
Impagidinium fenestroseptatum Head et al., 1989
Holotype:Head et al. 1989b, pl.2, fig.11-13
Locus typicus: ODP leg 105, dite 646, Labrador Sea
Stratum typicum: Early Pliocene
Original diagnosis: Head et al., 1989, p.458
Cysts proximochorate with spherical to subspherical outline. Central body smooth and thin walled. Parasutural crests robust and of constant height and suggest a gonyaulacacean tabulation. Oval fenestrations are developed in the crests and may be restricted to the distal half. Crest thickness may increase distally, and the crest top is T-shaped in cross section so as to form a narrow platform, the margins of which are irregular and sinuous in plan view. Paratabulation not determined precisely but appears similar to the genus Impagidinium. Archeopyle type not determined, although presumably precingular Type P.
Dimensions. Holotype: maximum overall diameter (i.e., including crests), 65 µm. Range of maximum overall diameter, 52(58)65 µm. Crest height about 6 to 10 µm; distal crest platform about 2 to 3 µm wide. Eleven specimens were measured.
Remarks. In many specimens the wall of the central body was not present, which resulted in a skeletal structure formed by the parasutural crests. In other specimens, the body wall was present but extremely thin, despite the well-preserved state of the assemblage as a whole. Consequently, the archeopyle was not recognized. The extremely thin central body of I. fenestroseptatum is presumably a primary feature.
Affinities:
Head et al., 1989, p.458: In I. fenestroseptatum, parasutural crests are fenestrate, whereas in both I. grandis (Davey, 1975) Jan du Chene et al., 1986 (from the Senonian) and 1. aquaeductum (Piasecki, 1980) Lentin and Williams, 1985 (from the Miocene), crest tops are supported by rows of more discretely formed processes. Pterodinium babatum Below, 1981 (O.C., pro. Pterodinium bab Below, 1981), described from Lower Cretaceous of Morocco, lacks distal crest platforms and a more angular outline than I. fenestroseptatum.
Holotype:Head et al. 1989b, pl.2, fig.11-13
Locus typicus: ODP leg 105, dite 646, Labrador Sea
Stratum typicum: Early Pliocene
Original diagnosis: Head et al., 1989, p.458
Cysts proximochorate with spherical to subspherical outline. Central body smooth and thin walled. Parasutural crests robust and of constant height and suggest a gonyaulacacean tabulation. Oval fenestrations are developed in the crests and may be restricted to the distal half. Crest thickness may increase distally, and the crest top is T-shaped in cross section so as to form a narrow platform, the margins of which are irregular and sinuous in plan view. Paratabulation not determined precisely but appears similar to the genus Impagidinium. Archeopyle type not determined, although presumably precingular Type P.
Dimensions. Holotype: maximum overall diameter (i.e., including crests), 65 µm. Range of maximum overall diameter, 52(58)65 µm. Crest height about 6 to 10 µm; distal crest platform about 2 to 3 µm wide. Eleven specimens were measured.
Remarks. In many specimens the wall of the central body was not present, which resulted in a skeletal structure formed by the parasutural crests. In other specimens, the body wall was present but extremely thin, despite the well-preserved state of the assemblage as a whole. Consequently, the archeopyle was not recognized. The extremely thin central body of I. fenestroseptatum is presumably a primary feature.
Affinities:
Head et al., 1989, p.458: In I. fenestroseptatum, parasutural crests are fenestrate, whereas in both I. grandis (Davey, 1975) Jan du Chene et al., 1986 (from the Senonian) and 1. aquaeductum (Piasecki, 1980) Lentin and Williams, 1985 (from the Miocene), crest tops are supported by rows of more discretely formed processes. Pterodinium babatum Below, 1981 (O.C., pro. Pterodinium bab Below, 1981), described from Lower Cretaceous of Morocco, lacks distal crest platforms and a more angular outline than I. fenestroseptatum.