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Apteodinium gerasimovii
From Fensome et al., 2019:
Apteodinium gerasimovii Iosifova, 1996, p.207,209, pl.3, figs.4a–b,6. Holotype: Iosifova, 1996, pl.3, figs.4a–b. Age: Ryazanian.
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Original description: [Iosifova 1996, p. 207, 209]:
Diagnosis:
A species of Apteodinium with long apical horn, comprising about a third of the length of the cyst. Wall two-layered. Endophragm smooth, periphragm discontinuous, strongly microperforated.
Description:
Gonyaulacoid cysts, subcircular, dorso-ventrally flattened, with a long blunt apical horn, composing about a third of the length of the cyst.
Wall two-layered. Endophragm smooth, periphragm discontinuous, strongly microperforated. Periphragm absent only on the antapical pole and parasulcus.
Apical horn is formed by both periphragm and endophragm. Endophragm forms a low bulge at the beginning of the horn. Periphragm forms a spongious extremity of the horn.
Paratabulation indicated by archeopyle, parasulcus and paracingulum only.
Paracingulum clearly visible. Parasulcus occasionally indicated by a broad depression on the hypocyst.
Archeopyle precingular, Type 3".
Dimensions:
Length: holotype: 87.5 µm, isotype: 81 µm, range: 93-81 µm; width: holotype: 75 µm, isotype: 62 µm, range: 36-80 µm; length of the apical horn: holotype: 25 µm, isotype: 17 µm, range: 27-17 µm. Five specimens measured.
Affinities/Comparison:
It differs from all other species of the genus by its very distinctive long apical horn in combination with the constitution of the wall. Apteodinium bucculiatum Davies, 1983 also has a long apical horn, but its autophragm is granular. Apteodinium spinosum Jain and Millipied, 1975 has a long apical horn and spinose periphragm.
Apteodinium gerasimovii Iosifova, 1996, p.207,209, pl.3, figs.4a–b,6. Holotype: Iosifova, 1996, pl.3, figs.4a–b. Age: Ryazanian.
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Original description: [Iosifova 1996, p. 207, 209]:
Diagnosis:
A species of Apteodinium with long apical horn, comprising about a third of the length of the cyst. Wall two-layered. Endophragm smooth, periphragm discontinuous, strongly microperforated.
Description:
Gonyaulacoid cysts, subcircular, dorso-ventrally flattened, with a long blunt apical horn, composing about a third of the length of the cyst.
Wall two-layered. Endophragm smooth, periphragm discontinuous, strongly microperforated. Periphragm absent only on the antapical pole and parasulcus.
Apical horn is formed by both periphragm and endophragm. Endophragm forms a low bulge at the beginning of the horn. Periphragm forms a spongious extremity of the horn.
Paratabulation indicated by archeopyle, parasulcus and paracingulum only.
Paracingulum clearly visible. Parasulcus occasionally indicated by a broad depression on the hypocyst.
Archeopyle precingular, Type 3".
Dimensions:
Length: holotype: 87.5 µm, isotype: 81 µm, range: 93-81 µm; width: holotype: 75 µm, isotype: 62 µm, range: 36-80 µm; length of the apical horn: holotype: 25 µm, isotype: 17 µm, range: 27-17 µm. Five specimens measured.
Affinities/Comparison:
It differs from all other species of the genus by its very distinctive long apical horn in combination with the constitution of the wall. Apteodinium bucculiatum Davies, 1983 also has a long apical horn, but its autophragm is granular. Apteodinium spinosum Jain and Millipied, 1975 has a long apical horn and spinose periphragm.