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Amphigymnium
From Williams et al., 2017:
[Amphigymnium, Lentin and Vozzhennikova, 1990, p. 28-29
Type species: originally as Amphidinium mitratum, Vozzhennikova, 1967 (pl.1, fig.2)] ; Amphigymnium mitratum, Lentin and Vozzhennikova, 1990
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Original description: [Lentin and Vozzhennikova, 1990]:
Description:
Fossil dinoflagellate cysts which are elongate oval in outline with a short, rounded to slightly conical epicyst and a long oval hypocyst. The extremely thin autophragm may be smooth, microporate or microgranulose; extremely delicate longitudinal ridges may be found on the epicyst but the hypocyst is without longitudinal ridges. 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 may be deep or shallow, dividing the cyst into two unequal portions or, when very shallow, without indentation; the epicyst being usually less than 1/3 the length of the hypocyst. The parasulcus is indicated by a shallow longitudinal depression, principally on the hypocyst immediately below the paracingulum.
Affinities:
Amphigymnium is separated from Dinogymnium by its oval shape and the thin, non costate autophragm. Species in this genus most closely resemble the modern genus Amphidinium. There are three species which were formerly placed in the genus Dinogymnium which we consider to belong to Amphigymnium.
[Amphigymnium, Lentin and Vozzhennikova, 1990, p. 28-29
Type species: originally as Amphidinium mitratum, Vozzhennikova, 1967 (pl.1, fig.2)] ; Amphigymnium mitratum, Lentin and Vozzhennikova, 1990
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lentin and Vozzhennikova, 1990]:
Description:
Fossil dinoflagellate cysts which are elongate oval in outline with a short, rounded to slightly conical epicyst and a long oval hypocyst. The extremely thin autophragm may be smooth, microporate or microgranulose; extremely delicate longitudinal ridges may be found on the epicyst but the hypocyst is without longitudinal ridges. 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 may be deep or shallow, dividing the cyst into two unequal portions or, when very shallow, without indentation; the epicyst being usually less than 1/3 the length of the hypocyst. The parasulcus is indicated by a shallow longitudinal depression, principally on the hypocyst immediately below the paracingulum.
Affinities:
Amphigymnium is separated from Dinogymnium by its oval shape and the thin, non costate autophragm. Species in this genus most closely resemble the modern genus Amphidinium. There are three species which were formerly placed in the genus Dinogymnium which we consider to belong to Amphigymnium.