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Prionodinium
From Williams et al., 2017:
[Prionodinium, Leffingwell and Morgan, 1977, p. 293-294
Type species: Prionodinium alaskense, Leffingwell and Morgan, 1977 ( pl.1, figs.2a–b)]
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Original description: [Leffingwell and Morgan, 1977]:
Description:
Elongate-oval proximate cysts, with an apical horn; double-layered wall closely appressed; distinct tabulation which is reflected by non-inflated septal crests under which no significant cavity is formed between the periphragm and endophragm; crests smooth, striate or alveolate; distal margin of crests slightly denticulate; fully or incompletely developed cingulum divides the cyst approximately into halves; reflected tabulation 4`, 6``, 6c, 5-6```, 1p, (ps) 1````; postsulcal plate sometimes reflected as separate plate; sulcus extends onto epitract; precingular plates elongate, with the exception of 6``, which is reduced in height and subtriangular; surface smooth or finely ornamented, and in some species, pustules are superimposed upon the fine ornamentation; precingular (3``) archeopyle, operculum free.
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Modified description:
Stover and Evitt, 1978, p. 181:
Synopsis:
Cysts proximate, elongate ellipsoidal, with or without an apical horn; paratabulation gonyaulacacean, indicated by parasutural septa; archeopyle precingular, Type P.
Description:
Shape: Elongate ellipsoidal.
Wall relationships: Endophragm and periphragm appressed, acavate.
Wall features: Smooth, striate, or alveolate parasutural septa typically well developed. Surface smooth or ornamented with features of low relief.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 6``, 6c, 5-6```, lp, 1````, ps.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six rectangular paraplates.
Parasulcus: Elongate area bordered by parasutural features; posterior paraplate may be differentiated.
Size: Intermediate.
Affinities:
Prionodinium differs from Carpodinium in having parasutural septa, rather than parasutural folds with septal crests, and in having the parasutural features well developed, and equally so, over the entire cyst.
[Prionodinium, Leffingwell and Morgan, 1977, p. 293-294
Type species: Prionodinium alaskense, Leffingwell and Morgan, 1977 ( pl.1, figs.2a–b)]
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Original description: [Leffingwell and Morgan, 1977]:
Description:
Elongate-oval proximate cysts, with an apical horn; double-layered wall closely appressed; distinct tabulation which is reflected by non-inflated septal crests under which no significant cavity is formed between the periphragm and endophragm; crests smooth, striate or alveolate; distal margin of crests slightly denticulate; fully or incompletely developed cingulum divides the cyst approximately into halves; reflected tabulation 4`, 6``, 6c, 5-6```, 1p, (ps) 1````; postsulcal plate sometimes reflected as separate plate; sulcus extends onto epitract; precingular plates elongate, with the exception of 6``, which is reduced in height and subtriangular; surface smooth or finely ornamented, and in some species, pustules are superimposed upon the fine ornamentation; precingular (3``) archeopyle, operculum free.
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Modified description:
Stover and Evitt, 1978, p. 181:
Synopsis:
Cysts proximate, elongate ellipsoidal, with or without an apical horn; paratabulation gonyaulacacean, indicated by parasutural septa; archeopyle precingular, Type P.
Description:
Shape: Elongate ellipsoidal.
Wall relationships: Endophragm and periphragm appressed, acavate.
Wall features: Smooth, striate, or alveolate parasutural septa typically well developed. Surface smooth or ornamented with features of low relief.
Paratabulation: Indicated by parasutural features; gonyaulacacean, formula: 4`, 6``, 6c, 5-6```, lp, 1````, ps.
Archeopyle: Precingular, Type P (3`` only); operculum free.
Paracingulum: Indicated by six rectangular paraplates.
Parasulcus: Elongate area bordered by parasutural features; posterior paraplate may be differentiated.
Size: Intermediate.
Affinities:
Prionodinium differs from Carpodinium in having parasutural septa, rather than parasutural folds with septal crests, and in having the parasutural features well developed, and equally so, over the entire cyst.