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Stephodinium
From Williams et al., 2017:
[Stephodinium, Deflandre, 1936a, p. 58. Emendation: Davey, 1970, p. 347.
Type species: Stephodinium coronatum, Deflandre, 1936 (text-fig.104)]
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Original description: [Deflandre, 1936a]: (Translation: Stover and Evitt, 1978, p. 192):
Let us add to these Stephodinium n.g. n.sp., whose equator bears a very special equatorial pad which is not known in any living form.
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Deflandre, 1936 (b), p. 171:
Supplemental description:
the genus is characterized by the presence of a very wide equatorial pad that seems to take the place of the transverse furrow.
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Emended description:
Davey, 1970:
Supplemental description:
Cavate cysts possessing an ovoidal inner body and surrounding periphragm membrane. Inner body and outer membrane in contact on ventral surface and at apex and antapex of shell. Maximum separation in cingular region. Apical horn usually present. tabulation present on outer membrane, sutures marked by low ridges. Archaeopyle precingular. (from Stover and Evitt, 1978, p. 192)
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Modified description:
Stover and Evitt, 1978, p. 192:
Synopsis:
Cysts camocavate; endocyst subspherical to ellipsoidal; perophragm appressed or close to endophragm in ventral, apical, and antapical areas, but separated elsewhere, with greatest separation in dorsal paracingular area; paratabulation indicated incompletely by parasutural ridges; archaeopyle precingular, Type P.
Description:
Shape: Endocyst subspherical to ellipsoidal; pericyst with dorsal bandlike equatorial extension; short apical horn may be present.
Wall relationships: Cysts camocavate; enophragm and periphragm appressed or close together apicall, antapically, and ventrally, but separated dorsally; pericoel widest at middorsal surfaces.
Wall features: Low parasutural ridges on periphragm may have finely denticulate crests; areas between ridges smooth or finely ornamented; endophragm smooth.
Paratabulation: Indicated incompletely by parasutural features and apparently expressed more clearly on epicyst than on pericyst; possibly gonyaulacacean, formula unknown.
Archaeopyle: Precingular, Type P (3`` only); transverse parasutural lines or low ridges. Position of paracingulum coincident with greatest separation of periphragm and endophragm.
parasulcus: Not indicated.
Size: Normally intermediate to large.
Affinities:
Stephodinium differs from Thalassiphora and Hystrichostrogylon in that its wall layers are appressd ventrally instead of dorsally. Further, Hystrichostrogylon has processes, which Stephodinium lacks.
[Stephodinium, Deflandre, 1936a, p. 58. Emendation: Davey, 1970, p. 347.
Type species: Stephodinium coronatum, Deflandre, 1936 (text-fig.104)]
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Original description: [Deflandre, 1936a]: (Translation: Stover and Evitt, 1978, p. 192):
Let us add to these Stephodinium n.g. n.sp., whose equator bears a very special equatorial pad which is not known in any living form.
---------------------------------------------------------------------------------------------------------------
Deflandre, 1936 (b), p. 171:
Supplemental description:
the genus is characterized by the presence of a very wide equatorial pad that seems to take the place of the transverse furrow.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Davey, 1970:
Supplemental description:
Cavate cysts possessing an ovoidal inner body and surrounding periphragm membrane. Inner body and outer membrane in contact on ventral surface and at apex and antapex of shell. Maximum separation in cingular region. Apical horn usually present. tabulation present on outer membrane, sutures marked by low ridges. Archaeopyle precingular. (from Stover and Evitt, 1978, p. 192)
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Modified description:
Stover and Evitt, 1978, p. 192:
Synopsis:
Cysts camocavate; endocyst subspherical to ellipsoidal; perophragm appressed or close to endophragm in ventral, apical, and antapical areas, but separated elsewhere, with greatest separation in dorsal paracingular area; paratabulation indicated incompletely by parasutural ridges; archaeopyle precingular, Type P.
Description:
Shape: Endocyst subspherical to ellipsoidal; pericyst with dorsal bandlike equatorial extension; short apical horn may be present.
Wall relationships: Cysts camocavate; enophragm and periphragm appressed or close together apicall, antapically, and ventrally, but separated dorsally; pericoel widest at middorsal surfaces.
Wall features: Low parasutural ridges on periphragm may have finely denticulate crests; areas between ridges smooth or finely ornamented; endophragm smooth.
Paratabulation: Indicated incompletely by parasutural features and apparently expressed more clearly on epicyst than on pericyst; possibly gonyaulacacean, formula unknown.
Archaeopyle: Precingular, Type P (3`` only); transverse parasutural lines or low ridges. Position of paracingulum coincident with greatest separation of periphragm and endophragm.
parasulcus: Not indicated.
Size: Normally intermediate to large.
Affinities:
Stephodinium differs from Thalassiphora and Hystrichostrogylon in that its wall layers are appressd ventrally instead of dorsally. Further, Hystrichostrogylon has processes, which Stephodinium lacks.