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Nelsoniella
From Williams et al., 2017:
[Nelsoniella, Cookson and Eisenack, 1960a, p. 4
Type species: Nelsoniella aceras, Cookson and Eisenack, 1960a (pl.1, fig.12)]
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Original description: [Cookson and Eisenack, 1960]:
Description:
Shell circular in outline, epithecal and hypothecal regions distinctly differentiated, not delimited by a girdle but by the anterior limit of the large capsule, which completely fills the hypotheca and causes the shell to bulge considerably on the ventral surface; the dorsal surface, marked by a prominent pylome, is slightly convex.The epitheca is variously sculptured and may or may not be provided with an apical horn. The wall of the hypotheca is smooth.
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Modified description:
Stover and Evitt, 1978, p. 114:
Synopsis:
Cysts proximate, epicavate, lenticular to subspherical, generally with a short apical horn and without an antapical horn or horns; wide apical pericoel only; periphragm and endophragm appressed elsewhere. Paratabulation indicated by archeopyle only; latter intercalary, Type l; archeopyle index 0.4 to 0.5.
Description:
Shape: Lenticular to subspherical, generally with a short apical horn; no antapical horn.
Wall Relationships: Cysts epicavate; endophragm and periphragm appressed in antapical one-half to two-thirds of cyst, widely separated elsewhere to form prominent apical pericoel; wall layers virtually indistinguishable where appressed.
Wall Features: No parasutural features. Periphragm smooth or variously ornamented with features of low to moderate relief; ornamentation usually confined to epicyst.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Intercalary, Type I or la (2a only); archeopyle index O.4 to O.5. Generally only antapical part of endoarcheopyle suture discernible.
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Nelsoniella differs from Xenikoon in having a large wide apical pericoel and usually a short apical horn. In Xenikoon, the apical pericoel is smaller (lower). Nelsoniella differs from Eucladinium, Eurydinium, and Isabelidinium in lacking an antapical pericoel and, additionally, from Eucladinium in not having an antapical protrusion.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Nelsoniella Cookson and Eisenack, 1960a. According to Stover and Evitt (1978, p.114), Nelsoniella is proximate, epicavate, lenticular to subspherical, generally with a short apical horn and without an antapical horn or horns; wide apical pericoel only; periphragm and endophragm appressed elsewhere. Paratabulation indicated by archeopyle only; latter intercalary. Type I, archeopyle index 0.4-0.5.
[Nelsoniella, Cookson and Eisenack, 1960a, p. 4
Type species: Nelsoniella aceras, Cookson and Eisenack, 1960a (pl.1, fig.12)]
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Original description: [Cookson and Eisenack, 1960]:
Description:
Shell circular in outline, epithecal and hypothecal regions distinctly differentiated, not delimited by a girdle but by the anterior limit of the large capsule, which completely fills the hypotheca and causes the shell to bulge considerably on the ventral surface; the dorsal surface, marked by a prominent pylome, is slightly convex.The epitheca is variously sculptured and may or may not be provided with an apical horn. The wall of the hypotheca is smooth.
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Modified description:
Stover and Evitt, 1978, p. 114:
Synopsis:
Cysts proximate, epicavate, lenticular to subspherical, generally with a short apical horn and without an antapical horn or horns; wide apical pericoel only; periphragm and endophragm appressed elsewhere. Paratabulation indicated by archeopyle only; latter intercalary, Type l; archeopyle index 0.4 to 0.5.
Description:
Shape: Lenticular to subspherical, generally with a short apical horn; no antapical horn.
Wall Relationships: Cysts epicavate; endophragm and periphragm appressed in antapical one-half to two-thirds of cyst, widely separated elsewhere to form prominent apical pericoel; wall layers virtually indistinguishable where appressed.
Wall Features: No parasutural features. Periphragm smooth or variously ornamented with features of low to moderate relief; ornamentation usually confined to epicyst.
Paratabulation: Indicated by archeopyle only.
Archeopyle: Intercalary, Type I or la (2a only); archeopyle index O.4 to O.5. Generally only antapical part of endoarcheopyle suture discernible.
Paracingulum: Not indicated.
Parasulcus: Not indicated.
Size: Intermediate to large.
Affinities:
Nelsoniella differs from Xenikoon in having a large wide apical pericoel and usually a short apical horn. In Xenikoon, the apical pericoel is smaller (lower). Nelsoniella differs from Eucladinium, Eurydinium, and Isabelidinium in lacking an antapical pericoel and, additionally, from Eucladinium in not having an antapical protrusion.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Nelsoniella Cookson and Eisenack, 1960a. According to Stover and Evitt (1978, p.114), Nelsoniella is proximate, epicavate, lenticular to subspherical, generally with a short apical horn and without an antapical horn or horns; wide apical pericoel only; periphragm and endophragm appressed elsewhere. Paratabulation indicated by archeopyle only; latter intercalary. Type I, archeopyle index 0.4-0.5.