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Heslertonia
From Williams et al., 2017:
[Heslertonia, Sarjeant, 1966b, p. 133; Emendation: Duxbury, 1980, p. 123
Type species: originally as Gonyaulax heslertonensis, Neale and Sarjeant, 1962 (pl.19, fig.5; text-fig.1)] ; Heslerotonia heslertonensis, Sarjeant, 1966; emend. Duxbury, 1980
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Original description: [Sarjeant, 1966]:
Diagnosis:
Chorate dinoflagellate cyst, spherical, ellipsoidal, ovoidal or polyhedral, with high sutural crests outlining the tabulation 3-4`, 0-1a, 6``, 6c, 6```, 1p, 0-1pv, 1````. Cingulum strongly or weakly helicoid; sulcus generally but not constantly extending on to epitract. Apical and antapical horns absent. Sutures perforate or imperforate; their distal edges smooth or denticulate. Crest height exceeds 1/4 of shell width. Surface smooth, granular, punctate, nodose or reticulate. Precingular archaeopyle formed by loss of plate 3``; archaeopyle sometimes absent.
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Modified description:
Stover and Evitt 1978, p. 160-161:
Synopsis:
Cysts proximochorate; body subspherical; paratabulation gonyaulacacean, indicated by high parasutural septa, height of which is greater than one-fourth main body diameter; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: Parasutural septa high, height greater than one-fourth main body diameter; smooth, perforate or imperforate, with finely denticulate or smooth distal margins. Autophragm between septa smooth or variously ornamented with features of low relief.
Paratabulation: Indicated by parasutural septa; gonyaulacacean, formula: 4`, 0-1a, 6``, 6c, 6```, 1p, 1````, 1s.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six paraplates.
Parasulcus: Expressed as a narrow longitudinally elongate area, mainly on hypocyst, bordered by parasutural septa.
Size: Small to intermediate
Affinities:
On Heslertonia the height of the parasutural features is >0.25 of body diameter; whereas on Impagidinium and Leptodinium, the height is <0.25 of body diameter. A better understanding of paratabulation details on Heslertonia and Pterodinium - as well as on possible transitional forms not too unlike Spiniferites cingulatus and S. pterotus - may eventually justify the suppression on Heslertonia.
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Emended description:
Duxbury, 1980:
Diagnosis:
Spheroidal to ovoidal dinoflagellate cysts bearing high, regular parasutural crests outlining a typically gonyaulacacean paratabulation pattern. The crests are higher than 1/4 the main body diameter and may vary in height on individual specimens. The main body surface is smooth to finely granular and the archeopyle is epicystal.
[Heslertonia, Sarjeant, 1966b, p. 133; Emendation: Duxbury, 1980, p. 123
Type species: originally as Gonyaulax heslertonensis, Neale and Sarjeant, 1962 (pl.19, fig.5; text-fig.1)] ; Heslerotonia heslertonensis, Sarjeant, 1966; emend. Duxbury, 1980
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Sarjeant, 1966]:
Diagnosis:
Chorate dinoflagellate cyst, spherical, ellipsoidal, ovoidal or polyhedral, with high sutural crests outlining the tabulation 3-4`, 0-1a, 6``, 6c, 6```, 1p, 0-1pv, 1````. Cingulum strongly or weakly helicoid; sulcus generally but not constantly extending on to epitract. Apical and antapical horns absent. Sutures perforate or imperforate; their distal edges smooth or denticulate. Crest height exceeds 1/4 of shell width. Surface smooth, granular, punctate, nodose or reticulate. Precingular archaeopyle formed by loss of plate 3``; archaeopyle sometimes absent.
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Modified description:
Stover and Evitt 1978, p. 160-161:
Synopsis:
Cysts proximochorate; body subspherical; paratabulation gonyaulacacean, indicated by high parasutural septa, height of which is greater than one-fourth main body diameter; archeopyle precingular, Type P.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: Parasutural septa high, height greater than one-fourth main body diameter; smooth, perforate or imperforate, with finely denticulate or smooth distal margins. Autophragm between septa smooth or variously ornamented with features of low relief.
Paratabulation: Indicated by parasutural septa; gonyaulacacean, formula: 4`, 0-1a, 6``, 6c, 6```, 1p, 1````, 1s.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six paraplates.
Parasulcus: Expressed as a narrow longitudinally elongate area, mainly on hypocyst, bordered by parasutural septa.
Size: Small to intermediate
Affinities:
On Heslertonia the height of the parasutural features is >0.25 of body diameter; whereas on Impagidinium and Leptodinium, the height is <0.25 of body diameter. A better understanding of paratabulation details on Heslertonia and Pterodinium - as well as on possible transitional forms not too unlike Spiniferites cingulatus and S. pterotus - may eventually justify the suppression on Heslertonia.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Duxbury, 1980:
Diagnosis:
Spheroidal to ovoidal dinoflagellate cysts bearing high, regular parasutural crests outlining a typically gonyaulacacean paratabulation pattern. The crests are higher than 1/4 the main body diameter and may vary in height on individual specimens. The main body surface is smooth to finely granular and the archeopyle is epicystal.