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Cristadinium diminutivum
Cristadinium diminutivum Head et al., 1989
Holotype: Head et al., 1989, pl.1, fig.8
Locus typicus: ODP leg 105, site 646, Labrador Sea
Stratum typicum: Late Miocene-earliest Pliocene
Diagnosis. Cysts small, proximate, autophragmal, dorsoventrally compressed and brown in color. Cyst length greater than width. Epicyst triangular and straight sided. Apical horn pointed (except at tip) and hollow. Hypocyst of equal length to, or slightly shorter than epicyst, with moderately to strongly convergent lateral margins, and having two antapical horns of equal length, which are slightly divergent to parallel and taper to acuminate solid tips. Lateral sides of hypocyst normally straight to slightly concave, but may be slightly convex. Wall surface granulate, with granules showing some longitudinal alignment. Very thin low crests with distinctively thickened bases occur along lateral margins of epicyst and hypocyst. Paracingulum planar, often indicated by one or more folds, and bearing a single crest similar to that of lateral margins. Archeopyle isodeltaform hexa-intercalary, involving paraplate 2a only. Operculum, free or possibly adherent.
Dimensions. Holotype: Cyst length, 45 Ám. Range in cyst length, 28(41.0)54 Ám. Crest height 0.5-1.5 Ám. Twenty-eight specimens were measured.
Description. Cysts have an angular outline with straight sides, except for the antapical margin separating the antapical horns, which varies from weakly to strongly concave. All specimens recorded were dorsoventrally compressed. Crests occur along the lateral margins of epicyst
and hypocyst and occupy most of the epicystal lateral margins and a vuiable proportion of the hypocystal lateral margins (generally the lower two thirds, as for the holotype, Pl. I, Fig. 8, and for the specimen illustrated in Pl. 1, Fig. 16). Crest bases form narrow but conspicuous thickenings and from these rise low, very thin and diaphanous crests of apparently even height. The paracingulum is indicated by a fold that may extend some distance above or below the equatorial line and that bears a single crest similar to those occuring on lateral margins. One or two narrow meridional folds were sometimes observed on the epicyst. Faint and discontinuous lines were occasionally observed on the hypocyst and may represent paratabulation. The operculum was found to be in place in most specimens (possibly adherent), although it was free in occasional specimens. The principal archeopyle suture is entire.
Discussion. This species is characterized by a combination of small size, narrow, angular outline, and low thin crests on lateral margins of epicyst and hypocyst.
Holotype: Head et al., 1989, pl.1, fig.8
Locus typicus: ODP leg 105, site 646, Labrador Sea
Stratum typicum: Late Miocene-earliest Pliocene
Diagnosis. Cysts small, proximate, autophragmal, dorsoventrally compressed and brown in color. Cyst length greater than width. Epicyst triangular and straight sided. Apical horn pointed (except at tip) and hollow. Hypocyst of equal length to, or slightly shorter than epicyst, with moderately to strongly convergent lateral margins, and having two antapical horns of equal length, which are slightly divergent to parallel and taper to acuminate solid tips. Lateral sides of hypocyst normally straight to slightly concave, but may be slightly convex. Wall surface granulate, with granules showing some longitudinal alignment. Very thin low crests with distinctively thickened bases occur along lateral margins of epicyst and hypocyst. Paracingulum planar, often indicated by one or more folds, and bearing a single crest similar to that of lateral margins. Archeopyle isodeltaform hexa-intercalary, involving paraplate 2a only. Operculum, free or possibly adherent.
Dimensions. Holotype: Cyst length, 45 Ám. Range in cyst length, 28(41.0)54 Ám. Crest height 0.5-1.5 Ám. Twenty-eight specimens were measured.
Description. Cysts have an angular outline with straight sides, except for the antapical margin separating the antapical horns, which varies from weakly to strongly concave. All specimens recorded were dorsoventrally compressed. Crests occur along the lateral margins of epicyst
and hypocyst and occupy most of the epicystal lateral margins and a vuiable proportion of the hypocystal lateral margins (generally the lower two thirds, as for the holotype, Pl. I, Fig. 8, and for the specimen illustrated in Pl. 1, Fig. 16). Crest bases form narrow but conspicuous thickenings and from these rise low, very thin and diaphanous crests of apparently even height. The paracingulum is indicated by a fold that may extend some distance above or below the equatorial line and that bears a single crest similar to those occuring on lateral margins. One or two narrow meridional folds were sometimes observed on the epicyst. Faint and discontinuous lines were occasionally observed on the hypocyst and may represent paratabulation. The operculum was found to be in place in most specimens (possibly adherent), although it was free in occasional specimens. The principal archeopyle suture is entire.
Discussion. This species is characterized by a combination of small size, narrow, angular outline, and low thin crests on lateral margins of epicyst and hypocyst.