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Sentusidinium
From Williams et al., 2017:
[Sentusidinium, Sarjeant and Stover, 1978, p. 49–50; Emendation: Courtinat, 1989, p. 192.
Tax. sr. syn.: Batiacasphaera, according to Dörhöfer and Davies (1980, p.40) — however, Lentin and Williams (1981, p.24,253) retained Sentusidinium.
Type species: originally as Tenua rioultii, Sarjeant, 1968 (pl.1, fig.22; pl.2, fig.1)] ; Sentusidinium rioultii, Sarjeant and Stover, 1978; emend. Courtinat, 1989
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Original description: [Sarjeant and Stover, 1978]:
Diagnosis:
Proximate to proximochorate cyst, subspherical to ellipsoidal; wall single-layered or apparently so, and bearing short, usually evenly distributed nontabular projections such as coarse granulae, tuberculae, baculae, or spines with blunt, acuminate, capitate or branched tips. These surface features are generally isolate, but some adjacent projections may have confluent bases and/or interconnected tips. The length of the projections is consistently less than one-half, and typically less than one-third, of the shortest diameter of the cyst.
Paratabulation is indicated mainly by the type A apical archaeopyle, whose principal suture is generally zigzag (although the angulation may not be readily apparent on uncompressed specimens). Short, longitudinally directed accessory archaeopyle sutures are frequently present, their positions denoting the anterior boundaries between precingular paraplates. The operculum is free, its constituent paraplates not differentiated. An equatorial alignment of some projections, delimiting a lightly ornamented or unornamented paracingulum, may sometimes be observed; but this is usually inconspicuous and may not be developed. Other indications of paratabulation are lacking.
Overall size is generally less than 100 μm.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subspherical to ellipsoidal body, rather than one that is dorsoventrally flattened; in lacking an offset parasutural notch; and in not having medial areas without, or with reduced, ornamentation. In addition, Sentusidinium lacks an apical angularity and antapical lobations; however, it should be stressed that these are not developed in all species of Cyclonephelium. Sentusidinium differs from Parvulodinium Dodekova (1975) by having nontabular rather than intratabular ornamentation.
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Modified description:
Stover and Evitt 1978, p. 80-81:
Synopsis:
Cysts proximate to proximochorate; subspherical autophragm bears numerous short, generally evenly distributed, normally isolated, nontabular projection; archeopyle apical, Type tA.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with numerous, generally evenly distributed and usually isolated nontabular features; these are most often short spines or cones, and may be granules, tubercules, bacules, or similar features of low to moderate relief.
Paratabulation: Generally indicated by archeopyle only, occasionally also by poorly delimited paracingulum.
Archeopyle: Apical, Type (tA); principal archeopyle suture zigzag; operculum free.
Paracingulum: Generally not indicated, or indicated by faint transverse alignment of nontabular features in the equatorial area.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subsphaerical body rather than a lenticular body, and in lacking the medial bald areas found on many species of Cyclonephelium.
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Emended description:
Courtinat, 1989: (Translation: LPP):
Diagnosis:
Subspherical to ovoidal apteate cyst with an autophragm only. The cyst has parasutural and intratabular processes. These processes may be joined at the bases or distally interconnected. The gonyaulacacean type paratabulation formula is, following the Kofoid notation: 4`, ?a, 6``, 6c, 6```, 1p, 1pv, 1````, ?s; following the Taylor-Evitt notation: A-C, 1u, ?K, au-fi, Iu-VI, X-Z, ?(ai, fu, Ii, Im). The operculum is free multiplated. The archaeopyle is apical type (tA); the accessory archaeopyle sutures are more or less well developed depending on the species.
[Sentusidinium, Sarjeant and Stover, 1978, p. 49–50; Emendation: Courtinat, 1989, p. 192.
Tax. sr. syn.: Batiacasphaera, according to Dörhöfer and Davies (1980, p.40) — however, Lentin and Williams (1981, p.24,253) retained Sentusidinium.
Type species: originally as Tenua rioultii, Sarjeant, 1968 (pl.1, fig.22; pl.2, fig.1)] ; Sentusidinium rioultii, Sarjeant and Stover, 1978; emend. Courtinat, 1989
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Sarjeant and Stover, 1978]:
Diagnosis:
Proximate to proximochorate cyst, subspherical to ellipsoidal; wall single-layered or apparently so, and bearing short, usually evenly distributed nontabular projections such as coarse granulae, tuberculae, baculae, or spines with blunt, acuminate, capitate or branched tips. These surface features are generally isolate, but some adjacent projections may have confluent bases and/or interconnected tips. The length of the projections is consistently less than one-half, and typically less than one-third, of the shortest diameter of the cyst.
Paratabulation is indicated mainly by the type A apical archaeopyle, whose principal suture is generally zigzag (although the angulation may not be readily apparent on uncompressed specimens). Short, longitudinally directed accessory archaeopyle sutures are frequently present, their positions denoting the anterior boundaries between precingular paraplates. The operculum is free, its constituent paraplates not differentiated. An equatorial alignment of some projections, delimiting a lightly ornamented or unornamented paracingulum, may sometimes be observed; but this is usually inconspicuous and may not be developed. Other indications of paratabulation are lacking.
Overall size is generally less than 100 μm.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subspherical to ellipsoidal body, rather than one that is dorsoventrally flattened; in lacking an offset parasutural notch; and in not having medial areas without, or with reduced, ornamentation. In addition, Sentusidinium lacks an apical angularity and antapical lobations; however, it should be stressed that these are not developed in all species of Cyclonephelium. Sentusidinium differs from Parvulodinium Dodekova (1975) by having nontabular rather than intratabular ornamentation.
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Modified description:
Stover and Evitt 1978, p. 80-81:
Synopsis:
Cysts proximate to proximochorate; subspherical autophragm bears numerous short, generally evenly distributed, normally isolated, nontabular projection; archeopyle apical, Type tA.
Description:
Shape: Body subspherical.
Wall relationships: Autophragm only.
Wall features: No parasutural features. Autophragm with numerous, generally evenly distributed and usually isolated nontabular features; these are most often short spines or cones, and may be granules, tubercules, bacules, or similar features of low to moderate relief.
Paratabulation: Generally indicated by archeopyle only, occasionally also by poorly delimited paracingulum.
Archeopyle: Apical, Type (tA); principal archeopyle suture zigzag; operculum free.
Paracingulum: Generally not indicated, or indicated by faint transverse alignment of nontabular features in the equatorial area.
Parasulcus: Not indicated.
Size: Small to intermediate.
Affinities:
Sentusidinium differs from Cyclonephelium in having a subsphaerical body rather than a lenticular body, and in lacking the medial bald areas found on many species of Cyclonephelium.
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Emended description:
Courtinat, 1989: (Translation: LPP):
Diagnosis:
Subspherical to ovoidal apteate cyst with an autophragm only. The cyst has parasutural and intratabular processes. These processes may be joined at the bases or distally interconnected. The gonyaulacacean type paratabulation formula is, following the Kofoid notation: 4`, ?a, 6``, 6c, 6```, 1p, 1pv, 1````, ?s; following the Taylor-Evitt notation: A-C, 1u, ?K, au-fi, Iu-VI, X-Z, ?(ai, fu, Ii, Im). The operculum is free multiplated. The archaeopyle is apical type (tA); the accessory archaeopyle sutures are more or less well developed depending on the species.