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Horologinella
From Fensome et al., 2019:
Horologinella, Cookson and Eisenack, 1962a, p.271.
Emendations: Stover and Evitt, 1978, p.53–54; Backhouse, 1988, p.90; Pestchevitskaya, 2006, p. S635.
Stover and Evitt (1978, p.54) considered that, of the species of Horologinella described to that date, only the "type species", Horologinella lineata, was a dinoflagellate. Pestchevitskaya (2006, p. S635) considered only Horologinella lineata and Horologinella anabarensis to be dinoflagellates.
Type: Cookson and Eisenack, 1962a, pl.37, figs.1–2, as Horologinella lineata.
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Original description: [Cookson and Eisenack, 1962]:
Description:
Shell small, slightly biconvex, roughly hourglass-shaped, with or without fields, smooth or sculptured.
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Emended description:
Stover and Evitt, 1978:
Synopsis:
Cysts proximate, outline subquadrate with deep equatorial constriction; paratabulation indicated by low parasutural ridges; archeopyle apical, type uncertain.
Description:
Shape: Outline subquadrate with rounded corners and deep, relatively narrow equatorial constriction.
Wall relationships: Autophragm only.
Wall features: Low parasutural ridges delimit paraplates; autophragm granulate or faintly ornamented.
Paratabulation: Indicated by parasutural features; formula unknown.
Archeopyle: Apical, type uncertain.
Paracingulum: Indicated by conspicuous equatorial constriction.
Parasulcus: Featureless area on midventral surface of hypocyst.
Size: Small.
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Backhouse, 1988:
Synopsis:
Cyst small, proximate quadrate to subquadrate with an equatorial constriction. Paratabulation expressed by low surface features; paratabulation formula: 6`, 7", 6c, 7", 2````, Xs; archeopyle apical, subcircular, operculum free.
Description:
Shape: Dorso-ventrally compressed, outline quadrate to subquadrate with rounded corners, lateral margins constricted.
Wall relationships: Autophragm only.
Wall features: Low parasutural ridges, nontabular ridges, grana, and fine punctae.
Archaeopyle: Apical, atypical, opening subcircular occupying most of plate 4` and parts of adjoining paraplates. Paratabulation indicated by parasutural features; formula: 6`, oa, 7", ?6c, 7```, 0p, 2````, Xs.
Paracingulum: Indicated by parasutural features and lateral constrictions.
Parasulcus: Indicated by parasutural features; several paraplates may be expressed.
Size: Small.
Affinities:
No similar forms with paratabulation and conspicuous paracingular constriction are known.
Horologinella, Cookson and Eisenack, 1962a, p.271.
Emendations: Stover and Evitt, 1978, p.53–54; Backhouse, 1988, p.90; Pestchevitskaya, 2006, p. S635.
Stover and Evitt (1978, p.54) considered that, of the species of Horologinella described to that date, only the "type species", Horologinella lineata, was a dinoflagellate. Pestchevitskaya (2006, p. S635) considered only Horologinella lineata and Horologinella anabarensis to be dinoflagellates.
Type: Cookson and Eisenack, 1962a, pl.37, figs.1–2, as Horologinella lineata.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Cookson and Eisenack, 1962]:
Description:
Shell small, slightly biconvex, roughly hourglass-shaped, with or without fields, smooth or sculptured.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Stover and Evitt, 1978:
Synopsis:
Cysts proximate, outline subquadrate with deep equatorial constriction; paratabulation indicated by low parasutural ridges; archeopyle apical, type uncertain.
Description:
Shape: Outline subquadrate with rounded corners and deep, relatively narrow equatorial constriction.
Wall relationships: Autophragm only.
Wall features: Low parasutural ridges delimit paraplates; autophragm granulate or faintly ornamented.
Paratabulation: Indicated by parasutural features; formula unknown.
Archeopyle: Apical, type uncertain.
Paracingulum: Indicated by conspicuous equatorial constriction.
Parasulcus: Featureless area on midventral surface of hypocyst.
Size: Small.
-------------------------------
Backhouse, 1988:
Synopsis:
Cyst small, proximate quadrate to subquadrate with an equatorial constriction. Paratabulation expressed by low surface features; paratabulation formula: 6`, 7", 6c, 7", 2````, Xs; archeopyle apical, subcircular, operculum free.
Description:
Shape: Dorso-ventrally compressed, outline quadrate to subquadrate with rounded corners, lateral margins constricted.
Wall relationships: Autophragm only.
Wall features: Low parasutural ridges, nontabular ridges, grana, and fine punctae.
Archaeopyle: Apical, atypical, opening subcircular occupying most of plate 4` and parts of adjoining paraplates. Paratabulation indicated by parasutural features; formula: 6`, oa, 7", ?6c, 7```, 0p, 2````, Xs.
Paracingulum: Indicated by parasutural features and lateral constrictions.
Parasulcus: Indicated by parasutural features; several paraplates may be expressed.
Size: Small.
Affinities:
No similar forms with paratabulation and conspicuous paracingular constriction are known.