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Apteodinium apiatum
Apteodinium apiatum, McIntyre and Brideaux, 1980
Holotype: McIntyre and Brideaux, 1980, pl.2, figs.1-2; Jan du Chêne et al., 1986, pl.13, figs.7-8
Locus typicus: Martin Creek, District of Mackenzie, Canada
Stratum typicum: Valanginian, Lower Cretaceous
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Original description: [McIntyre and Brideaux, 1980, p. 11-12]:
Diagnosis:
Shape: Pericyst - Ambitus rounded-rhombic to subovoid, longer than broad; prolonged into a short apical horn, apparently solid and distally rounded, 4-10 µm in length. Slight dorsoventral compression. Endocyst - Ambitus rounded-rhombic to subovoid; apex and antapex rounded. Similar compression. Pericoels - Pericyst and endocyst in close contact except at the apex where the apical horn, formed by the pericyst, projects above the endocyst.
Phragma: Periphragm - 0.5-1.0 µm thick, commonly much folded. Surface ornament of low, pustulate elements 0.5-1.0 µm high and wide, verrucate in profile, but open to the endophragm in plan view in places on some specimens. Periphragm smooth or scabrate between pustules. Endophragm: Less than 0.5 µm thick, commonly much folded. Surface smooth or scabrate.
Paratabulation: Pericyst - A few specimens bear indistinct markings which appear parasutural; paratabulation otherwise indeterminable except in the vicinity of the archeopyle.
Pericingulum: Faint markings and/or folds delimit the pericingulum of the dorsal pericyst and, less distinctly on the ventral pericyst.
Perisulcus: Not observed.
Endocyst: Paratabulation not observed.
Archeopyle: Precingular, type P(3"). Operculum simple, free, rounded-polygonal and somewhat elongate in shape.
Variation: Density of the pustules on the periphragm variable; periphragm sculpture strongly reduced on some specimens. The morphology of the pustules suggests that they may have borne small apiculate extensions which have been removed by mechanical or chemical means.
Dimensions:
Pericyst length - 95-110 µm, width 80-90 µm.
Affinities:
The granular periphragm of Apteodinium maculatum Eisenack and Cookson bears variably grouped maculate sculpture elements. The pustulate sculpture elements on the smooth to scabrate periphragm of Apteodinium apiatum are variable in density but evenly spaced.
Holotype: McIntyre and Brideaux, 1980, pl.2, figs.1-2; Jan du Chêne et al., 1986, pl.13, figs.7-8
Locus typicus: Martin Creek, District of Mackenzie, Canada
Stratum typicum: Valanginian, Lower Cretaceous
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [McIntyre and Brideaux, 1980, p. 11-12]:
Diagnosis:
Shape: Pericyst - Ambitus rounded-rhombic to subovoid, longer than broad; prolonged into a short apical horn, apparently solid and distally rounded, 4-10 µm in length. Slight dorsoventral compression. Endocyst - Ambitus rounded-rhombic to subovoid; apex and antapex rounded. Similar compression. Pericoels - Pericyst and endocyst in close contact except at the apex where the apical horn, formed by the pericyst, projects above the endocyst.
Phragma: Periphragm - 0.5-1.0 µm thick, commonly much folded. Surface ornament of low, pustulate elements 0.5-1.0 µm high and wide, verrucate in profile, but open to the endophragm in plan view in places on some specimens. Periphragm smooth or scabrate between pustules. Endophragm: Less than 0.5 µm thick, commonly much folded. Surface smooth or scabrate.
Paratabulation: Pericyst - A few specimens bear indistinct markings which appear parasutural; paratabulation otherwise indeterminable except in the vicinity of the archeopyle.
Pericingulum: Faint markings and/or folds delimit the pericingulum of the dorsal pericyst and, less distinctly on the ventral pericyst.
Perisulcus: Not observed.
Endocyst: Paratabulation not observed.
Archeopyle: Precingular, type P(3"). Operculum simple, free, rounded-polygonal and somewhat elongate in shape.
Variation: Density of the pustules on the periphragm variable; periphragm sculpture strongly reduced on some specimens. The morphology of the pustules suggests that they may have borne small apiculate extensions which have been removed by mechanical or chemical means.
Dimensions:
Pericyst length - 95-110 µm, width 80-90 µm.
Affinities:
The granular periphragm of Apteodinium maculatum Eisenack and Cookson bears variably grouped maculate sculpture elements. The pustulate sculpture elements on the smooth to scabrate periphragm of Apteodinium apiatum are variable in density but evenly spaced.