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Vozzhennikovia
From Fensome et al., 2019:
Vozzhennikovia Lentin and Williams, 1976, p.65–66. Emendation: Sluijs et al., 2009, p.48–49.
Taxonomic senior synonym: Dioxya, according to Morgan (1977, p.131) -- however, Lentin and Williams (1981, p.287) retained Vozzhennikovia.
Bradford and Wall (1984, p.48) considered Trinovantedium to be a questionable taxonomic junior synonym of this genus. Type: Wilson, 1967a, figs.3–4, as Spinidinium apertura.
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Original description: [Lentin and Williams, 1976]:
Description:
Pericyst: Ambitus rounded to ovoidal. Apex occasionally rounded, more frequently produced into a short apical horn which distally may be acuminate, oblate or invaginated. Antapex rounded or commonly with one eccentrically located left antapical horn. Rarely there are two symmetrically located antapical horns which are unequal in length, the right antapical horn being reduced or vestigial. Epipericyst and hypopericyst of more or less equal size or epipericyst somewhat larger. Ambital outline widest in pericingular region. Compression dorso-ventral, moderate to extreme.
Endocyst: Ambitus rounded to ovoidal, almost always appressed against pericyst apart from in the vicinity of the horns. Usually difficult to delineate. Compression dorso-ventral, often extreme.
Pericoels: A small apical pericoel in the vicinity of the apical horn. If an antapical horn is present there may be a small antapical pericoel. Periphragm: Epipericyst and hypopericyst ornamented with nontabular echinae or processes rarely exceeding 10µm in length. The processes may be distally acuminate, oblate or invaginated. Processes often oriented in pericingular or perisulcal regions only.
Endophragm: Laevigate. Usually thin and difficult to delineate.
Pericyst: Paratabulation never discernible other than in the vicinity of the periarcheopyle.
Pericingulum: Generally present and indented. Planar or slightly helicoidal. Anterior and posterior parasutures delineated by a continuous or discontinuous row of echinae or processes. Area of pericingulum within parasutures is devoid of a surface ornamentation.
Perisulcus: Commonly delineated by absence of ornamentation. Indented. Extending onto epipericyst but considerably longer and wider on the hypopericyst reaching almost to the antapex.
Endocyst: Paratabulation not observed.
Standard hexa or broad hexa intercalary [archeopyle] resulting from the partial or complete detachment of the anterior intercalary paraplate 2a. The operculum may be free or remain attached along parasuture H4. Since the endophragm and periphragm are appressed in the vicinity of the archeopyle, there is no separation of the endoperculum and perioperculum so that effectively there is one archeopyle and one operculum. Transverse archeopyle index is 0.33-0.50. Transverse archeopyle ratio is 0.50-1.0.
Archeopyle Formula: I.
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Modified description:
Stover and Evitt, 1978, p. 130
Synopsis:
Cysts proximochorate, generally cornucavate, compressed peridinioid to nearly lenticular, with an apical horn, a usually well-developed left antapical horn, and a reduced right antapical horn; periphragm has numerous nontabular spines or processes; paratabulation indicated by archeopyle only, or by paracingulum and archeopyle; latter intercalary, Type I or la; archeopyle index <0.5.
Description:
Shape: Compressed peridinioid to nearly lenticular with a short apical and a usually distinct left antapical horn; right antapical horn commonly reduced or absent.
Wall relationships: Cysts generally cornucavate, rarely circumcavate
Wall features: No parasutural features. Periphragm ornamented with nontabular processes or spines; endophragm smooth.
Paratabulation: Indicated by archeopyle only, or by archeopyle and paracingulum.
Archeopyle: Intercalary, Type I or la (2a only); operculum free or attached; archeopyle index <0.5, generally 0.3 to 0.4.
Paracingulum: Indicated in equatorial area by transverse alignment of ornamentation into two parallel rows that may delimit a shallow concavity.
Parasulcus: Generally poorly expressed by a shallow depression, mainly on the hypocyst, and by the absence of ornamentation.
Size: Small to intermediate.
Affinities:
Vozzhennikovia differs from Spinidinium in that it has nontabular ornamentation rather than ornamentation arranged in penitabular rows or intratabular clusters, or both.
Vozzhennikovia Lentin and Williams, 1976, p.65–66. Emendation: Sluijs et al., 2009, p.48–49.
Taxonomic senior synonym: Dioxya, according to Morgan (1977, p.131) -- however, Lentin and Williams (1981, p.287) retained Vozzhennikovia.
Bradford and Wall (1984, p.48) considered Trinovantedium to be a questionable taxonomic junior synonym of this genus. Type: Wilson, 1967a, figs.3–4, as Spinidinium apertura.
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Original description: [Lentin and Williams, 1976]:
Description:
Pericyst: Ambitus rounded to ovoidal. Apex occasionally rounded, more frequently produced into a short apical horn which distally may be acuminate, oblate or invaginated. Antapex rounded or commonly with one eccentrically located left antapical horn. Rarely there are two symmetrically located antapical horns which are unequal in length, the right antapical horn being reduced or vestigial. Epipericyst and hypopericyst of more or less equal size or epipericyst somewhat larger. Ambital outline widest in pericingular region. Compression dorso-ventral, moderate to extreme.
Endocyst: Ambitus rounded to ovoidal, almost always appressed against pericyst apart from in the vicinity of the horns. Usually difficult to delineate. Compression dorso-ventral, often extreme.
Pericoels: A small apical pericoel in the vicinity of the apical horn. If an antapical horn is present there may be a small antapical pericoel. Periphragm: Epipericyst and hypopericyst ornamented with nontabular echinae or processes rarely exceeding 10µm in length. The processes may be distally acuminate, oblate or invaginated. Processes often oriented in pericingular or perisulcal regions only.
Endophragm: Laevigate. Usually thin and difficult to delineate.
Pericyst: Paratabulation never discernible other than in the vicinity of the periarcheopyle.
Pericingulum: Generally present and indented. Planar or slightly helicoidal. Anterior and posterior parasutures delineated by a continuous or discontinuous row of echinae or processes. Area of pericingulum within parasutures is devoid of a surface ornamentation.
Perisulcus: Commonly delineated by absence of ornamentation. Indented. Extending onto epipericyst but considerably longer and wider on the hypopericyst reaching almost to the antapex.
Endocyst: Paratabulation not observed.
Standard hexa or broad hexa intercalary [archeopyle] resulting from the partial or complete detachment of the anterior intercalary paraplate 2a. The operculum may be free or remain attached along parasuture H4. Since the endophragm and periphragm are appressed in the vicinity of the archeopyle, there is no separation of the endoperculum and perioperculum so that effectively there is one archeopyle and one operculum. Transverse archeopyle index is 0.33-0.50. Transverse archeopyle ratio is 0.50-1.0.
Archeopyle Formula: I.
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Modified description:
Stover and Evitt, 1978, p. 130
Synopsis:
Cysts proximochorate, generally cornucavate, compressed peridinioid to nearly lenticular, with an apical horn, a usually well-developed left antapical horn, and a reduced right antapical horn; periphragm has numerous nontabular spines or processes; paratabulation indicated by archeopyle only, or by paracingulum and archeopyle; latter intercalary, Type I or la; archeopyle index <0.5.
Description:
Shape: Compressed peridinioid to nearly lenticular with a short apical and a usually distinct left antapical horn; right antapical horn commonly reduced or absent.
Wall relationships: Cysts generally cornucavate, rarely circumcavate
Wall features: No parasutural features. Periphragm ornamented with nontabular processes or spines; endophragm smooth.
Paratabulation: Indicated by archeopyle only, or by archeopyle and paracingulum.
Archeopyle: Intercalary, Type I or la (2a only); operculum free or attached; archeopyle index <0.5, generally 0.3 to 0.4.
Paracingulum: Indicated in equatorial area by transverse alignment of ornamentation into two parallel rows that may delimit a shallow concavity.
Parasulcus: Generally poorly expressed by a shallow depression, mainly on the hypocyst, and by the absence of ornamentation.
Size: Small to intermediate.
Affinities:
Vozzhennikovia differs from Spinidinium in that it has nontabular ornamentation rather than ornamentation arranged in penitabular rows or intratabular clusters, or both.