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Vectidinium stoveri
From Fensome et al., 2019:
Vectidium stoveri Liengjarern et al., 1980, p.490–491, pl.54, fig.7.
Holotype: Liengjarern et al., 1980, pl.54, fig.7; Fensome et al., 1995, fig.1 — p.1807.
Originally (and now) Vectidinium, subsequently Phthanoperidinium.
Lentin and Williams (1985, p.365) retained this species in Vectidinium.
Age: Late Eocene–Early Oligocene.
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Locus typcus: Whitecliff Bay, Isle ol Wight, England
Stratum typicum: Late Eocene-Early Oligocene
Original diagnosis: Liengjarern et al., 1980, p.490
As for the genus: 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"", 0c, 5""", 2"""", 0s. 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.
Original description: Liengjarern et al., 1980, p.490-491
The dorso-ventral compression of these cysts is normally slight, and some specimens may be oriented in apical or antapical view; in lateral view the cysts are somewhat fusiform or oval. The epicyst has strongly convex sides which may merge imperceptibly in a very short, blunt apical horn with a solid tip on which sits a pore; the apical horn may be absent, and the epicyst apex is then invaginate. The hypocyst is commonly broadly rounded posteriorly, but some specimens may show a weak bilobation on the antapex. The short, eccentrically located left antapical horn may be present or absent.
The ornament varies in density and shape. When the ornament is baculate or of short processes their distal endings are often T-shaped and may be linked to those from near-by processes, giving the appearance of a tectum supported by columellae in optical section; sometimes the ornament is very reduced in size and mostly consisting of granules. The ornament may be densely or sparsely arranged on the paraplate surface. the most peripheral elements tending to be arranged along simulate rings. Laevigate pandasutural zones, usually narrow, are present but are not always clearly visible.
Cingulum and sulcus are distinct, both being marked by low ridges or folds on the autophragm. The cingulum is relatively wide, slightly helicoid or circular, not indented; intratabular ornament and smooth pandasutural zones may be observable on the cingular surface, but the number of cingular paraplates has not been determined with certainty. The sulcus is also broad and shallow, and extends approximately half-way to the apex. The shape and relative size of individual paraplates are difficult to determine because of very small size and transparent autophragm of these cysts.
When present, the archeopyle is formed by complete detachment of plates 1a, 3a, 3" - 5". On some specimens, accessory archeopyle sutures develop along most of the anterior margin of the cingulum, but both portions of the cyst usually remain attached along a narrow band, presumably corresponding to the sulcus. The operculum is always free, but it has not been possible to determine whether this is formed by a single piece or is compound, since isolated opercula have not been observed a fact suggesting that the operculum may be compound, disintegrating into the very small individual paraplates which would easily be lost in sieving of the organic residue during preparation.
Measurements. Holotype, autocyst length 37 µm, breadth 42 µm, apical horn 1 µm, left antapical horn 1 µm, width of cingulum 4 µm.
Range. Autocyst length 30(35.5)41 µm, breadth 24.5(31)42 µm, apical horn 0(2)4.2 µm, left antapical horn 0(1)4.5 µm, width of cingulum 2.7(3.6)4 µm. 24 specimens measured.
Vectidium stoveri Liengjarern et al., 1980, p.490–491, pl.54, fig.7.
Holotype: Liengjarern et al., 1980, pl.54, fig.7; Fensome et al., 1995, fig.1 — p.1807.
Originally (and now) Vectidinium, subsequently Phthanoperidinium.
Lentin and Williams (1985, p.365) retained this species in Vectidinium.
Age: Late Eocene–Early Oligocene.
---------------------------------------------------------------------------------------------------
Locus typcus: Whitecliff Bay, Isle ol Wight, England
Stratum typicum: Late Eocene-Early Oligocene
Original diagnosis: Liengjarern et al., 1980, p.490
As for the genus: 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"", 0c, 5""", 2"""", 0s. 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.
Original description: Liengjarern et al., 1980, p.490-491
The dorso-ventral compression of these cysts is normally slight, and some specimens may be oriented in apical or antapical view; in lateral view the cysts are somewhat fusiform or oval. The epicyst has strongly convex sides which may merge imperceptibly in a very short, blunt apical horn with a solid tip on which sits a pore; the apical horn may be absent, and the epicyst apex is then invaginate. The hypocyst is commonly broadly rounded posteriorly, but some specimens may show a weak bilobation on the antapex. The short, eccentrically located left antapical horn may be present or absent.
The ornament varies in density and shape. When the ornament is baculate or of short processes their distal endings are often T-shaped and may be linked to those from near-by processes, giving the appearance of a tectum supported by columellae in optical section; sometimes the ornament is very reduced in size and mostly consisting of granules. The ornament may be densely or sparsely arranged on the paraplate surface. the most peripheral elements tending to be arranged along simulate rings. Laevigate pandasutural zones, usually narrow, are present but are not always clearly visible.
Cingulum and sulcus are distinct, both being marked by low ridges or folds on the autophragm. The cingulum is relatively wide, slightly helicoid or circular, not indented; intratabular ornament and smooth pandasutural zones may be observable on the cingular surface, but the number of cingular paraplates has not been determined with certainty. The sulcus is also broad and shallow, and extends approximately half-way to the apex. The shape and relative size of individual paraplates are difficult to determine because of very small size and transparent autophragm of these cysts.
When present, the archeopyle is formed by complete detachment of plates 1a, 3a, 3" - 5". On some specimens, accessory archeopyle sutures develop along most of the anterior margin of the cingulum, but both portions of the cyst usually remain attached along a narrow band, presumably corresponding to the sulcus. The operculum is always free, but it has not been possible to determine whether this is formed by a single piece or is compound, since isolated opercula have not been observed a fact suggesting that the operculum may be compound, disintegrating into the very small individual paraplates which would easily be lost in sieving of the organic residue during preparation.
Measurements. Holotype, autocyst length 37 µm, breadth 42 µm, apical horn 1 µm, left antapical horn 1 µm, width of cingulum 4 µm.
Range. Autocyst length 30(35.5)41 µm, breadth 24.5(31)42 µm, apical horn 0(2)4.2 µm, left antapical horn 0(1)4.5 µm, width of cingulum 2.7(3.6)4 µm. 24 specimens measured.