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Alterbidinium montanaense
Alterbidinium montanaensis, (Harland, 1977), Lentin and Williams, 1985
Holotype: Harland, 1977, pl.25, figs.4,7
Locus typicus: Fort Peck Reservoir, Montana, U.S.A.
Age: Late Campanian-Maastrichtian.
Stratum typicum: ?Campanian to Maastrichtian
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Original description as Deflandrea montanaensis: [Harland, 1977, p. 184]:
Diagnosis:
Cavate cyst, epitract conical, hypotract hemispheroidal with an asymmetrical "skirt" and horn. Endoblast elongated apically and hemispheroidal antapically. Wall layers smooth. Apex surmounted by a bifid tip; the larger antapical horn acuminate.
Tabulation discernible but not usually recognizable, delimited by low, smooth, or poorly denticulate ridges.
Cingulum planar, may or may not be slightly indented; sulcus large and broad, widening towards the antapex.
Archeopyle intercalary in periphragm and endophragm; commonly attached Ia/Ia (Evitt 1967), and apically/antapically elongate hexagonal in shape.
Description:
A diamond-shaped to elongate fusiform cyst made up of the two wall layers that are only adpressed in the cingular region and on the upper part of the hypotract. The epitractal periphragm is drawn out into an apical horn which carries a dorso-ventrally flattened, bifid tip. The antapical "skirt" and horn sometimes carry small, poorly developed, irregular spines, especially on the margin of the "skirt".
The tabulation is variously developed but difficult to decipher, it is probably ?4", 1a, ?7", 6c, ?""", ?2"""". The cingulum is divided into six well-defined cingular plates.
Archeopyle is formed by a single opening through the periphragm and endophragm and the operculum appears to remain attached (Pl. 25, fig. 10), type Ia/Ia of Evitt (1967).
Dimensions:
Holotype: length 35.0 µm, breadth 16.25 µm.
Holotype: Harland, 1977, pl.25, figs.4,7
Locus typicus: Fort Peck Reservoir, Montana, U.S.A.
Age: Late Campanian-Maastrichtian.
Stratum typicum: ?Campanian to Maastrichtian
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Original description as Deflandrea montanaensis: [Harland, 1977, p. 184]:
Diagnosis:
Cavate cyst, epitract conical, hypotract hemispheroidal with an asymmetrical "skirt" and horn. Endoblast elongated apically and hemispheroidal antapically. Wall layers smooth. Apex surmounted by a bifid tip; the larger antapical horn acuminate.
Tabulation discernible but not usually recognizable, delimited by low, smooth, or poorly denticulate ridges.
Cingulum planar, may or may not be slightly indented; sulcus large and broad, widening towards the antapex.
Archeopyle intercalary in periphragm and endophragm; commonly attached Ia/Ia (Evitt 1967), and apically/antapically elongate hexagonal in shape.
Description:
A diamond-shaped to elongate fusiform cyst made up of the two wall layers that are only adpressed in the cingular region and on the upper part of the hypotract. The epitractal periphragm is drawn out into an apical horn which carries a dorso-ventrally flattened, bifid tip. The antapical "skirt" and horn sometimes carry small, poorly developed, irregular spines, especially on the margin of the "skirt".
The tabulation is variously developed but difficult to decipher, it is probably ?4", 1a, ?7", 6c, ?""", ?2"""". The cingulum is divided into six well-defined cingular plates.
Archeopyle is formed by a single opening through the periphragm and endophragm and the operculum appears to remain attached (Pl. 25, fig. 10), type Ia/Ia of Evitt (1967).
Dimensions:
Holotype: length 35.0 µm, breadth 16.25 µm.