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Yolkinigymnium
From Williams et al., 2017:
[Yolkinigymnium Lentin and Vozzhennikova, 1990, p. 30-31
Type species: originally Dinogymnium lanceolatum, May, 1977 (pl.2, figs.9–10); Yolkinigymnium lanceolatum, Lentin and Vozzhennikova, 1990]
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Original description: [Lentin and Vozzhennikova, 1990]:
Description:
Fossil dinoflagellate cysts which are extremely long and narrow with the epicyst much shorter than the hypocyst, with pointed apex and rounded to pointed antapex (Cingulum Index = 15-30). The autophragm may be smooth, granulose or microporate with indistinct longitudinal ridges or folds.
The archeopyle is formed by two arcuate sutures of equal length which result in the loss of a single paraplate on the apex of the cyst.
The paracingulum is deep to shallow, dividing the cyst into two very unequal portions, the epicyst being less than 1/4 the length of the hypocyst. Parasulcus may be indicated by a shallow longitudinal depression principally on the hypocyst immediately below the paracingulum.
Affinities:
Yolkinigymnium is separated from Dinogymnium by the extremely long narrow shape and the thin, non-costate autophragm. Although no archeopyle was observed by May (1977) on the type specimen of Y. lanceolatum, it has been observed in specimens of the same species from Canada. There are two species which were formerly placed in the genus Dinogymnium which we consider to belong to Yolkinigymnium.
[Yolkinigymnium Lentin and Vozzhennikova, 1990, p. 30-31
Type species: originally Dinogymnium lanceolatum, May, 1977 (pl.2, figs.9–10); Yolkinigymnium lanceolatum, Lentin and Vozzhennikova, 1990]
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Original description: [Lentin and Vozzhennikova, 1990]:
Description:
Fossil dinoflagellate cysts which are extremely long and narrow with the epicyst much shorter than the hypocyst, with pointed apex and rounded to pointed antapex (Cingulum Index = 15-30). The autophragm may be smooth, granulose or microporate with indistinct longitudinal ridges or folds.
The archeopyle is formed by two arcuate sutures of equal length which result in the loss of a single paraplate on the apex of the cyst.
The paracingulum is deep to shallow, dividing the cyst into two very unequal portions, the epicyst being less than 1/4 the length of the hypocyst. Parasulcus may be indicated by a shallow longitudinal depression principally on the hypocyst immediately below the paracingulum.
Affinities:
Yolkinigymnium is separated from Dinogymnium by the extremely long narrow shape and the thin, non-costate autophragm. Although no archeopyle was observed by May (1977) on the type specimen of Y. lanceolatum, it has been observed in specimens of the same species from Canada. There are two species which were formerly placed in the genus Dinogymnium which we consider to belong to Yolkinigymnium.