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Palaeotetradinium
From Williams et al., 2017:
[Palaeotetradinium, Deflandre, 1936b, p. 189. Emendations: Deflandre and Sarjeant, 1970, p. 3, 4; Stover and Evitt, 1978, p. 70.
Tax. jr. syn.: Rhombodella according to Stover and Evitt (1978, p.70–71) — however, Duxbury (1980, p.134–135) retained Rhombodella.
This name was not validly published in Deflandre (1934, caption to fig.6 — p.967) since no description was provided.
Type species: Palaeotetradinium silicorum, Deflandre, 1936b (pl.9, fig.11)] ; emend. Morgenroth, 1968; emend. Deflandre and Sarjeant, 1970
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Original description: [Deflandre, 1936]: (Translation: Stover and Evitt, 1978, p. 70):
Description:
The shell, whose membrane has the appearance close to that of many Palaeoperidinium from flints, is shaped as a tetrahedron with concave faces. It does not seem to have definite polarity.
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Morgenroth, 1968, p. 553: (Translation: Stover and Evitt, 1978, p. 70):
Emended description of type species:
Outer shell tetrahedral, thin walled, weakly granulate. The tetrahedron points are always relatively short, never attenuate. Through staining (in this case fuchsin was used as stain!) a delicate inner capsule becomes visible, which mimics the outer shell, except that it extends only incompletely into its points. None of the numerous specimens bears an opening. Nor was a girdle furrow or anything similar observed. All specimens constantly show 4 points.
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Emended descriptions:
Deflandre and Sarjeant, 1970: (Translation: Stover and Evitt, 1978, p.70):
Description:
Shell of small size, grossly tetrahedral, extended along the line of the cingulum and with the antapex somewhat flattened. Tabulation discernible, with the sutures between the plates marked by low crests; two large postcingular plates recognizable on the dorsal surface. Epitheca (epitract) smaller and tapering in a more pronounced manner.
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Stover and Evitt, 1978:
Synopsis:
Cysts proximate, circumcavate; pericyst outline diamond-shaped with triangular endocyst almost completely filling the epicyst; archeopyle antapex, type uncertain.
Description:
Shape: Pericyst outline diamond-shaped, angles acute to rounded; somewhat compressed dorso-ventrally.
Wall relationships: Cysts circumcavate; roundly triangular endocyst confined to and nearly filling epicyst.
Wall features: No parasutural features. Periphragm and endophragm smooth, or with features of low relief; few to numerous spinules may occur at or near the angles. Periphragm normally develops median longitudinal fold on one surface, and one or more transverse equatorial folds on the opposite surface.
Paratabulation: Essentially not indicated.
Archeopyle: At apex, openings in periphragm and endophragm; sutures straight, slightly concave, or jagged; opercula free or possibly attached.
Paracingulum: Essentially not indicated; lateral extremities of pericyst and faint equatorial transverse folds at or near the base of the epicyst may be interpreted as expressions of a paracingulum.
Parasulcus: Not indicated.
Size: Small.
Affinities:
Palaeotetradinium differs from Trigonopyxidia in having a quadrate rate rather than a triangular outline and in having the endocyst confined to the anterior part of the pericyst.
[Palaeotetradinium, Deflandre, 1936b, p. 189. Emendations: Deflandre and Sarjeant, 1970, p. 3, 4; Stover and Evitt, 1978, p. 70.
Tax. jr. syn.: Rhombodella according to Stover and Evitt (1978, p.70–71) — however, Duxbury (1980, p.134–135) retained Rhombodella.
This name was not validly published in Deflandre (1934, caption to fig.6 — p.967) since no description was provided.
Type species: Palaeotetradinium silicorum, Deflandre, 1936b (pl.9, fig.11)] ; emend. Morgenroth, 1968; emend. Deflandre and Sarjeant, 1970
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Deflandre, 1936]: (Translation: Stover and Evitt, 1978, p. 70):
Description:
The shell, whose membrane has the appearance close to that of many Palaeoperidinium from flints, is shaped as a tetrahedron with concave faces. It does not seem to have definite polarity.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Morgenroth, 1968, p. 553: (Translation: Stover and Evitt, 1978, p. 70):
Emended description of type species:
Outer shell tetrahedral, thin walled, weakly granulate. The tetrahedron points are always relatively short, never attenuate. Through staining (in this case fuchsin was used as stain!) a delicate inner capsule becomes visible, which mimics the outer shell, except that it extends only incompletely into its points. None of the numerous specimens bears an opening. Nor was a girdle furrow or anything similar observed. All specimens constantly show 4 points.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Deflandre and Sarjeant, 1970: (Translation: Stover and Evitt, 1978, p.70):
Description:
Shell of small size, grossly tetrahedral, extended along the line of the cingulum and with the antapex somewhat flattened. Tabulation discernible, with the sutures between the plates marked by low crests; two large postcingular plates recognizable on the dorsal surface. Epitheca (epitract) smaller and tapering in a more pronounced manner.
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Stover and Evitt, 1978:
Synopsis:
Cysts proximate, circumcavate; pericyst outline diamond-shaped with triangular endocyst almost completely filling the epicyst; archeopyle antapex, type uncertain.
Description:
Shape: Pericyst outline diamond-shaped, angles acute to rounded; somewhat compressed dorso-ventrally.
Wall relationships: Cysts circumcavate; roundly triangular endocyst confined to and nearly filling epicyst.
Wall features: No parasutural features. Periphragm and endophragm smooth, or with features of low relief; few to numerous spinules may occur at or near the angles. Periphragm normally develops median longitudinal fold on one surface, and one or more transverse equatorial folds on the opposite surface.
Paratabulation: Essentially not indicated.
Archeopyle: At apex, openings in periphragm and endophragm; sutures straight, slightly concave, or jagged; opercula free or possibly attached.
Paracingulum: Essentially not indicated; lateral extremities of pericyst and faint equatorial transverse folds at or near the base of the epicyst may be interpreted as expressions of a paracingulum.
Parasulcus: Not indicated.
Size: Small.
Affinities:
Palaeotetradinium differs from Trigonopyxidia in having a quadrate rate rather than a triangular outline and in having the endocyst confined to the anterior part of the pericyst.