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Apteodinium granuliferum
Apteodinium granuliferum, Iosifova, 1996
Holotype: Iosifova 1996: Plate XVIII, 2a-c
Isotypes: Iosifova 1996: Plate XIII, 3a,b; Plate XV, 6a-c
Locus typicus: Tchernaya Retchka outcrop, the Ryazan district, Russia.
Occurrence: Tchernaya Retchka outcrop, the Ryazanian, R. riasanensis ammonite zone and deposits of probable Hauterivian age.
Stratum typicum: the Ryazanian, R. riasanensis ammonite zone.
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Original description: [Iosifova 1996, p. 209, 211]:
Diagnosis:
Cysts of moderate size, egg-shaped with small conical apical horn. Cysts wall moderately thick, endophragm and periphragm closely adpressed over the whole surface of the cyst. Periphragm densely granular. Any traces of paratabulation are generally absent. The parasulcus is occasionally visible as a depression on the hypocyst.
Archeopyle precingular, Type 3". Operculum free.
Description:
Gonyaulacoid cyst egg-shaped, slightly dorso-ventrally flattened, with small conical apical horn. Epicyst and hypocyst are of equal size, epicyst conical, hypocyst hemispherical. Thickness of the wall is about 1 µm, endophragm and periphragm are best defined and closely adpressed over the whole surface of the cyst. Periphragm densely granular. Traces of paratabulation are generally absent. The parasulcus is visible as a depression on the hypocyst only in one specimen (Plate XV, 6a-c).
Archeopyle precingular, Type 3". Operculum free.
Dimensions:
Length: holotype: 44 µm, range: 36-44 µm; width: holotype: 34 µm, range: 33-34 µm. Five specimens measured.
Remarks:
Apteodinium granuliferum Iosifova, sp. nov. resembles Operculodinium Wall, 1967, but differs from it by the presence of the apical horn. Chytroeisphaeridia (Sarjeant, 1962) Downie and Sarjeant, 1965 emend. Davey, 1979b has a smooth hyaline autophragmal wall.
Affinities/Comparison:
A. granuliferum resembles Apteodinium maculatum Eisenack and Cookson, 1960, but differs from it by the shape of the apical horn, smaller size and constitution of the wall (endophragm and periphragm in the new species are well defined and phragm is thicker). Apteodinium granulatum Eisenack, 1958 emend. Lucas-Clark, 1987 is much larger, has much longer apical horn and thicker two-layered wall.
Apteodinium syzygia (Dorhofer and Davies, 1980) Stover and Williams, 1987 has much thicker wall, which is fibrous in optical section. The new species differs from ?Chytroeisphaeridia gochtii (Dodekova, 1975) Jansonius, 1986 by its densely granular periphragm.
Holotype: Iosifova 1996: Plate XVIII, 2a-c
Isotypes: Iosifova 1996: Plate XIII, 3a,b; Plate XV, 6a-c
Locus typicus: Tchernaya Retchka outcrop, the Ryazan district, Russia.
Occurrence: Tchernaya Retchka outcrop, the Ryazanian, R. riasanensis ammonite zone and deposits of probable Hauterivian age.
Stratum typicum: the Ryazanian, R. riasanensis ammonite zone.
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Original description: [Iosifova 1996, p. 209, 211]:
Diagnosis:
Cysts of moderate size, egg-shaped with small conical apical horn. Cysts wall moderately thick, endophragm and periphragm closely adpressed over the whole surface of the cyst. Periphragm densely granular. Any traces of paratabulation are generally absent. The parasulcus is occasionally visible as a depression on the hypocyst.
Archeopyle precingular, Type 3". Operculum free.
Description:
Gonyaulacoid cyst egg-shaped, slightly dorso-ventrally flattened, with small conical apical horn. Epicyst and hypocyst are of equal size, epicyst conical, hypocyst hemispherical. Thickness of the wall is about 1 µm, endophragm and periphragm are best defined and closely adpressed over the whole surface of the cyst. Periphragm densely granular. Traces of paratabulation are generally absent. The parasulcus is visible as a depression on the hypocyst only in one specimen (Plate XV, 6a-c).
Archeopyle precingular, Type 3". Operculum free.
Dimensions:
Length: holotype: 44 µm, range: 36-44 µm; width: holotype: 34 µm, range: 33-34 µm. Five specimens measured.
Remarks:
Apteodinium granuliferum Iosifova, sp. nov. resembles Operculodinium Wall, 1967, but differs from it by the presence of the apical horn. Chytroeisphaeridia (Sarjeant, 1962) Downie and Sarjeant, 1965 emend. Davey, 1979b has a smooth hyaline autophragmal wall.
Affinities/Comparison:
A. granuliferum resembles Apteodinium maculatum Eisenack and Cookson, 1960, but differs from it by the shape of the apical horn, smaller size and constitution of the wall (endophragm and periphragm in the new species are well defined and phragm is thicker). Apteodinium granulatum Eisenack, 1958 emend. Lucas-Clark, 1987 is much larger, has much longer apical horn and thicker two-layered wall.
Apteodinium syzygia (Dorhofer and Davies, 1980) Stover and Williams, 1987 has much thicker wall, which is fibrous in optical section. The new species differs from ?Chytroeisphaeridia gochtii (Dodekova, 1975) Jansonius, 1986 by its densely granular periphragm.