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Votadinium calvum
From Fensome et al., 2019:
Votadinium calvum Reid, 1977
Motile equivalent: Peridinium (now Protoperidinium) oblongum (Aurivillius, 1898) Cleve, 1900, according to Reid (1977, p.444).
For a discussion of the nomenclatural validity and legitimacy of this species name, see the discussion under Votadinium.
Holotype: Reid, 1977, pl.2, fig.21; Fensome et al., 1993a, fig.1 — p.1017.
Locus typicus: Dee Estuary, England
Stratum typicum: Holocene
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Original diagnosis: Reid, 1977, p.444
Test "heart shaped" with two antapical lobes separated by a shallow antapical depression in dorsoventral view. Trapezoidal in lateral view. Length and breadth almost equal. Wall thin 1 µm and single layered, usually with a smooth surface but surface may be microgranular. Intercalary archeopyle truncating the apex obliquely.
Original description: Reid, 1977, p.444-445
The two sides of the cyst are symmetrical and mirror images. There are no antapical or apical thickenings of the wall and only one specimen showed surface ornamentation in the form of low irregular granae. Careful observation under phase contrast showed "crater-like" pits on many specimens. The operculum may remain attached at the apex and is sixsided with a length: breath ratio of 0.9:1. Short cracks may develop at right angles to the archeopyle suture indicating the position of the precingular plates. The angular flap-like apex that remains after the archeopyle opens may split down the middle to facilitate dehiscence. In many specimens an inner thin hyaline layer enclosing cytoplasm was seen. It is usually retracted from the outer cyst but has a similar shape.
Size: Holotype: 59 x 71 µm. Range of 15 specimens: 54-72 x 74 µm.
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[Remarks from Gurdebeke et al., 2019]:
Motile stage equivalent. Protoperidinium latidorsale Balech, according to Sarai et al. (2013).
Remarks. The specimen in Plate 1, figures 1–3 shows the general characteristics of the species: broad (wider than long) heart-shaped cyst with a thin wall and broadly rounded antapical horns separated by a shallow antapical concavity. The surface may be smooth (Plate 1, figures 4–7) or microgranular (Plate 1, figures 1–3). The SEM images (Plate 1, figures 4–7) show that the cyst presented here is deformed, which somewhat alters the appearance of its outline in ventral or dorsal view (e.g. depth of the antapical concavity or the shape of the horns). It is not known how general this phenomenon is, however, or whether the deformation took place before settling, in the sediment or during processing. The defining characteristics of the species remain valid. The SEM images (Plate 1, figures 4–7) also show sutural delineations suggesting that the entire apex is involved in archeopyle formation or that the apex is not clearly distinguishable. The archeopyle reflects a hexagonal dorsal intercalary plate (cf. the large 1a plate, Sarai et al. 2013). Although the apex is involved in the formation of the hexagonal archeopyle, it probably does not involve apical plates, as more than sutures would be expected in that case. A flagellar scar is present on the right side of the sulcal depression (Plate 1, figures 5, 7).
Comparison with other species. Votadinium calvum differs from V. spinosum by the absence of spines, from V. rhomboideum by its well-rounded shape, and from all other species in the genus by having the apex involved in the archeopyle. Specimens of Quinquecuspis concreta have been incorrectly identified as V. calvum in cases of poor cyst orientation (e.g. Matsuoka 1987, pl. 8, figs 1–3; McMinn 1991, pl. 1, figs 6 and 8).
Distribution and stratigraphic range. The modern distribution is global. Reports published with illustrations are mainly limited to latest Pleistocene to recent sediments. Older occurrences have been reported up to Burdigalian age (Londeix and Jan du Chêne 1998) but these are not illustrated so the identification cannot be confirmed.
Votadinium calvum Reid, 1977
Motile equivalent: Peridinium (now Protoperidinium) oblongum (Aurivillius, 1898) Cleve, 1900, according to Reid (1977, p.444).
For a discussion of the nomenclatural validity and legitimacy of this species name, see the discussion under Votadinium.
Holotype: Reid, 1977, pl.2, fig.21; Fensome et al., 1993a, fig.1 — p.1017.
Locus typicus: Dee Estuary, England
Stratum typicum: Holocene
---------------------------------------------------------------------------------------------------
Original diagnosis: Reid, 1977, p.444
Test "heart shaped" with two antapical lobes separated by a shallow antapical depression in dorsoventral view. Trapezoidal in lateral view. Length and breadth almost equal. Wall thin 1 µm and single layered, usually with a smooth surface but surface may be microgranular. Intercalary archeopyle truncating the apex obliquely.
Original description: Reid, 1977, p.444-445
The two sides of the cyst are symmetrical and mirror images. There are no antapical or apical thickenings of the wall and only one specimen showed surface ornamentation in the form of low irregular granae. Careful observation under phase contrast showed "crater-like" pits on many specimens. The operculum may remain attached at the apex and is sixsided with a length: breath ratio of 0.9:1. Short cracks may develop at right angles to the archeopyle suture indicating the position of the precingular plates. The angular flap-like apex that remains after the archeopyle opens may split down the middle to facilitate dehiscence. In many specimens an inner thin hyaline layer enclosing cytoplasm was seen. It is usually retracted from the outer cyst but has a similar shape.
Size: Holotype: 59 x 71 µm. Range of 15 specimens: 54-72 x 74 µm.
----------------------------------------------------------------------------------------------------------------------------------
[Remarks from Gurdebeke et al., 2019]:
Motile stage equivalent. Protoperidinium latidorsale Balech, according to Sarai et al. (2013).
Remarks. The specimen in Plate 1, figures 1–3 shows the general characteristics of the species: broad (wider than long) heart-shaped cyst with a thin wall and broadly rounded antapical horns separated by a shallow antapical concavity. The surface may be smooth (Plate 1, figures 4–7) or microgranular (Plate 1, figures 1–3). The SEM images (Plate 1, figures 4–7) show that the cyst presented here is deformed, which somewhat alters the appearance of its outline in ventral or dorsal view (e.g. depth of the antapical concavity or the shape of the horns). It is not known how general this phenomenon is, however, or whether the deformation took place before settling, in the sediment or during processing. The defining characteristics of the species remain valid. The SEM images (Plate 1, figures 4–7) also show sutural delineations suggesting that the entire apex is involved in archeopyle formation or that the apex is not clearly distinguishable. The archeopyle reflects a hexagonal dorsal intercalary plate (cf. the large 1a plate, Sarai et al. 2013). Although the apex is involved in the formation of the hexagonal archeopyle, it probably does not involve apical plates, as more than sutures would be expected in that case. A flagellar scar is present on the right side of the sulcal depression (Plate 1, figures 5, 7).
Comparison with other species. Votadinium calvum differs from V. spinosum by the absence of spines, from V. rhomboideum by its well-rounded shape, and from all other species in the genus by having the apex involved in the archeopyle. Specimens of Quinquecuspis concreta have been incorrectly identified as V. calvum in cases of poor cyst orientation (e.g. Matsuoka 1987, pl. 8, figs 1–3; McMinn 1991, pl. 1, figs 6 and 8).
Distribution and stratigraphic range. The modern distribution is global. Reports published with illustrations are mainly limited to latest Pleistocene to recent sediments. Older occurrences have been reported up to Burdigalian age (Londeix and Jan du Chêne 1998) but these are not illustrated so the identification cannot be confirmed.