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Vectidinium
From Williams et al., 2017:
[Vectidinium, Liengjarern et al. 1980, p. 490
Tax. sr. syn.: Phthanoperidinium, according to Islam (1982, p.313) — however, Lentin and Williams (1985, p.364) retained Vectidinium.
Type species: Vectidinium stoveri, Liengjarern et al., 1980 (pl.54, fig.7)]
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Original description: [Liengjarern et al., 1980]:
Diagnosis:
Single-walled proximate peridinioid cysts, moderately compressed dorso-ventrally, ambitus subpentagonal or subcircular to oval or somewhat fusiform. Epicyst and hypocyst of approximately equal size. Epicyst may or may not extend into a short apical horn; apical pore always present. Hypocyst semicircular or bilobed; left antapical horn present or absent, right antapical horn commonly present. Autophragm with atabular or intratabular to penitabular ornament of small granules, spinules or baculae, which may be reduced in size and/or number. Narrow laevigate pandasutural zones may be observable.
Paratabulation formula, when determinable, 4`, 3a, 7``, Oc, 5```, 2````, Os [sic]. When observable paraplate 1`` is rhombic, anteroposteriorly elongate, and relatively large.
Cingulum and sulcus distinct. The cingulum is wide relative to over-all autocyst size, not indented, nonor moderately helicoid.
Sulcus shallow and broad on the hypocyst.
Archeopyle combination type 3I3P 3``-5``, accessory sutures may occur along cingular margin of the remaining precingular paraplates. Opercula free.
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Modified description:
Stover and Williams, 1987, p. 225:
Synopsis:
Cysts proximate, slightly compressed dorsoventrally, outline subcircular to peridinioid; autophragm ornamentation nontabular or intratabular to penitabular, consists of features of low relief; paratabulation formula: 4`, 3a, 7", Xc, 5```, 2````, Xs; paratabulation not always discernible; archeopyle combined intercalary and precingular, type 3I3P, opercula not observed.
Description:
Shape: Outline subcircular to peridinioid in dorsal -ventral view; any or all horns may be absent; body compressed slightly dorsoventrally.
Wall relationships: Autophragm only.
Wall features: Ornamentation consists of nontabular features of low relief (granules, spines, bacules, short processes), or of features arranged in penitabular rows or intratabular clusters; some projections may be connected distally.
Archeopyle: Combined intercalary and precingular, type 3I3P; opercular not observed; accessory sutures reported as occurring along the cingular margins of the remaining precingulars.
Paratabulation: Indicated by intratabular and/or penitabular features; formula 4`, 3a, 7", 2````, Xs; paratabulation not always evident.
Paracingulum: Marked by low ridges or folds; planar or only slightly offset.
Parasulcus: Also delineated by low ridges or folds; confined mainly to hypocyst.
Size: Small, length about 30 to 40 μm.
Affinities:
Vectidinium differs from Laciniadinium Mclntyre 1975 in having free opercula. In Laciniadinium the single 3I3P@ opercular piece remains adnate along its cingular margin. Cysts of Luxadinium Brideaux and Mclntyre 1975, which also have 3I3P opercula, are cavate. Morkallacysta Harris 1974, like Vectidinium, has an autophragm only but possesses a 3I archeopyle and more prominent horns.
[Vectidinium, Liengjarern et al. 1980, p. 490
Tax. sr. syn.: Phthanoperidinium, according to Islam (1982, p.313) — however, Lentin and Williams (1985, p.364) retained Vectidinium.
Type species: Vectidinium stoveri, Liengjarern et al., 1980 (pl.54, fig.7)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Liengjarern et al., 1980]:
Diagnosis:
Single-walled proximate peridinioid cysts, moderately compressed dorso-ventrally, ambitus subpentagonal or subcircular to oval or somewhat fusiform. Epicyst and hypocyst of approximately equal size. Epicyst may or may not extend into a short apical horn; apical pore always present. Hypocyst semicircular or bilobed; left antapical horn present or absent, right antapical horn commonly present. Autophragm with atabular or intratabular to penitabular ornament of small granules, spinules or baculae, which may be reduced in size and/or number. Narrow laevigate pandasutural zones may be observable.
Paratabulation formula, when determinable, 4`, 3a, 7``, Oc, 5```, 2````, Os [sic]. When observable paraplate 1`` is rhombic, anteroposteriorly elongate, and relatively large.
Cingulum and sulcus distinct. The cingulum is wide relative to over-all autocyst size, not indented, nonor moderately helicoid.
Sulcus shallow and broad on the hypocyst.
Archeopyle combination type 3I3P 3``-5``, accessory sutures may occur along cingular margin of the remaining precingular paraplates. Opercula free.
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Modified description:
Stover and Williams, 1987, p. 225:
Synopsis:
Cysts proximate, slightly compressed dorsoventrally, outline subcircular to peridinioid; autophragm ornamentation nontabular or intratabular to penitabular, consists of features of low relief; paratabulation formula: 4`, 3a, 7", Xc, 5```, 2````, Xs; paratabulation not always discernible; archeopyle combined intercalary and precingular, type 3I3P, opercula not observed.
Description:
Shape: Outline subcircular to peridinioid in dorsal -ventral view; any or all horns may be absent; body compressed slightly dorsoventrally.
Wall relationships: Autophragm only.
Wall features: Ornamentation consists of nontabular features of low relief (granules, spines, bacules, short processes), or of features arranged in penitabular rows or intratabular clusters; some projections may be connected distally.
Archeopyle: Combined intercalary and precingular, type 3I3P; opercular not observed; accessory sutures reported as occurring along the cingular margins of the remaining precingulars.
Paratabulation: Indicated by intratabular and/or penitabular features; formula 4`, 3a, 7", 2````, Xs; paratabulation not always evident.
Paracingulum: Marked by low ridges or folds; planar or only slightly offset.
Parasulcus: Also delineated by low ridges or folds; confined mainly to hypocyst.
Size: Small, length about 30 to 40 μm.
Affinities:
Vectidinium differs from Laciniadinium Mclntyre 1975 in having free opercula. In Laciniadinium the single 3I3P@ opercular piece remains adnate along its cingular margin. Cysts of Luxadinium Brideaux and Mclntyre 1975, which also have 3I3P opercula, are cavate. Morkallacysta Harris 1974, like Vectidinium, has an autophragm only but possesses a 3I archeopyle and more prominent horns.