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Isabelidinium cingulatum
From Fensome et al., 2019:
Isabelidinium cingulatum Wilson, 1988, p.25, pl.14, figs.3,4a–c. Holotype: Wilson, 1988, pl.14, figs.4a–c; Fensome et al., 1996, figs.1–3 — p.2091. Age: Paleocene.
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Original description Wilson, 1988
DERIVATION OF NAME Latin, cingulum, belt, girdle; with reference to the relatively prominent paracingulum.
HOLOTYPE Sample V22/f8692 (L12087), Slide SM3101; Plate 14, Fig. 4, Teurian Stage (Paleocene); Waipawa Section, Hawkes Bay, New Zealand, grid reference V22/153341.
DESCRIPTION Cyst of intermediate size, bicavate, outline longitudinally elongate. Weil developed subtriangular apical pericoel and subrectangular antapical pericoel. Apex somewhat conical without horn; antapex broad and flat, without horns or with short pointed left antapical horn. Periphragm thin, finely reticulate and sometimes longitudinally striate; endocyst subcircular, thin-walled, finely reticulate or smooth. Archeopyle intercalary, Type la, relatively narrow (archeopyle index 0.5); operculum usually attached antapically. Paracingulum characteristically well developed (breadth 5-7 /Lm) defined by low parallel ridges on periphragm. Parasulcus indicated by termination of paracingulum on ventral surface and sometimes by narrow depression on ventral hypocyst. Partial paratabulation defined by archeopyle, paracingulum, and by somewhat vague low parasutural ridges.
DlSTRIBUTION Recorded only from the type locality; fairly rare.
DIMENSIONS Holotype: overall length 71 µm, breadth 54 µm, length of endocyst 42 /Lm, breadth 44 µm. Range: overall length 59 (68) 85 µm, breadth 49 (56) 66 µm (n= 10)
REMARKS The relatively prominent paracingulum is a major characteristic feature of this species. Other distinguishing features include the microreticulate periphragm and the generally broad, flat antapex. The species is also smaller than most previously described species of lsabelidinium.
Isabelidinium cingulatum Wilson, 1988, p.25, pl.14, figs.3,4a–c. Holotype: Wilson, 1988, pl.14, figs.4a–c; Fensome et al., 1996, figs.1–3 — p.2091. Age: Paleocene.
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Original description Wilson, 1988
DERIVATION OF NAME Latin, cingulum, belt, girdle; with reference to the relatively prominent paracingulum.
HOLOTYPE Sample V22/f8692 (L12087), Slide SM3101; Plate 14, Fig. 4, Teurian Stage (Paleocene); Waipawa Section, Hawkes Bay, New Zealand, grid reference V22/153341.
DESCRIPTION Cyst of intermediate size, bicavate, outline longitudinally elongate. Weil developed subtriangular apical pericoel and subrectangular antapical pericoel. Apex somewhat conical without horn; antapex broad and flat, without horns or with short pointed left antapical horn. Periphragm thin, finely reticulate and sometimes longitudinally striate; endocyst subcircular, thin-walled, finely reticulate or smooth. Archeopyle intercalary, Type la, relatively narrow (archeopyle index 0.5); operculum usually attached antapically. Paracingulum characteristically well developed (breadth 5-7 /Lm) defined by low parallel ridges on periphragm. Parasulcus indicated by termination of paracingulum on ventral surface and sometimes by narrow depression on ventral hypocyst. Partial paratabulation defined by archeopyle, paracingulum, and by somewhat vague low parasutural ridges.
DlSTRIBUTION Recorded only from the type locality; fairly rare.
DIMENSIONS Holotype: overall length 71 µm, breadth 54 µm, length of endocyst 42 /Lm, breadth 44 µm. Range: overall length 59 (68) 85 µm, breadth 49 (56) 66 µm (n= 10)
REMARKS The relatively prominent paracingulum is a major characteristic feature of this species. Other distinguishing features include the microreticulate periphragm and the generally broad, flat antapex. The species is also smaller than most previously described species of lsabelidinium.