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Heslertonia
From Fensome et al., 2019:
Heslertonia, Sarjeant, 1966b, p.133.
Emendation: Duxbury, 1980, p.123.
Type: Neale and Sarjeant, 1962, pl.19, fig.5; text-fig.1, as Gonyaulax heslertonensis.
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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: Neale and Sarjeant, 1962, pl.19, fig.5; text-fig.1, as Gonyaulax heslertonensis.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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.