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Ovoidinium epelidosphaeroides
From Fensome et al., 2019:
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Original description Nøhr-Hansen et al., 2017: figures 1–16; figures 10–12
Citation1993 Ovoidinium sp. 2; Nøhr-Hansen, p. 92, pl. 16, figs 5–8.
Derivation of name: ‘epelidosphaeroides’ refers to the morphological relation of this species to Epelidosphaeridia, indicated by the existence of intermediate morphotypes between both taxa.
Holotype: figure 1, GGU sample no. 522081-4 EF Z21-2.
Type locality: Section 30 of Nøhr-Hansen Citation1993 and GEUS PAL-3/2011, Tværdal, Geographical Society Ø, North-East Greenland (72°58’N, 23°02’E).
Diagnosis: A bicavate species of Ovoidinium with a pentagonal ambital outline, a short apical horn and one or two reduced antapical horns, of which the right is commonly vestigial. Cingulum marked on the dorsal face by a flange. Sulcus indicated by low ridges or folds, straight and very wide. Periphragm smooth (figures 1–12) or bearing a few short, solid sutural processes with a simple or buccinate tip. Tabulation not or only poorly expressed. Archaeopyle tAtI (1’–4’ + 1a–3a) with a wide suture which is slightly angulose on the dorsal face (, figures 2, 11; figure 11), and gently curved to symmetrically subtriangular on the ventral face.
Description: Medium-sized, dorsoventrally compressed bicavate cysts. The pericyst ambitus is subpentagonal, slightly asymmetrical. The epicyst ambitus is triangular, terminating in a short apical horn that is distally blunt and occasionally bears an apical pore. The hypocyst, commonly larger than the epicyst, is trapezoidal with a slanted antapex. The left antapical horn is broad, distally acuminate and may be reduced; the right antapical horn is reduced or absent. The endocyst ambitus is circular to elliptical. Peri- and endophragm are in contact along the central portions of the cyst but separate anteriorly and posteriorly to form pericoels of variable width. Periphragm hyaline, smooth or with faint longitudinal striations. The periphragm may bear a small number of solid, rod-like, 1–3 µm long, sutural processes with a simple, buccinate or capitate tip, and sometimes also partially developed low, sutural ridges (figures 13–16; figure 10). The endophragm is smooth.
The cingulum is marked on the dorsal side by a prominent flange, formed by a fold on the periphragm. A double row of sparse processes distributed along incomplete sutural ridges is often observable on the cyst's ventral face. The sulcus, flanked by distally smooth or denticulate ridges, is broad, straight (longitudinally aligned with the cyst central axis), and moderately indented, and occupies most of the ventral face (figure 1;, figure 10).
Archaeopyle type tAtI (1’–4’ + 1a–3a), wide. The precingular edge of the three intercalary plates is often reflected by a distinct tripartite indentation centrally located on the archaeopyle's dorsal suture, and/or a corresponding tripartite dorsal opercular margin. On the ventral face, the archaeopyle suture is generally smooth and straight or gently curved. Occasionally, a short, subtriangular, tongue-like projection, which corresponds to the posterior edge of apical plate 1’, can be seen on the ventral opercular margin. The operculum is simple, free or adherent.
Tabulation partially expressed by the cingulum, the archaeopyle suture and the distribution of the ornament when present. Nodular inclusions (omphali, or biopolymeric accumulation bodies; Evitt Citation1985), often occur on the inner ventral side of the endocyst (e.g., figures 1, 3, 13).
Dimensions
Greenland specimens:
Holotype: Pericyst length 74 µm, breadth 66 µm; endocyst, 51 µm × 51 µm; apical horn 7 µm; antapical horns, left 8 µm, right 2 µm.
Range: Pericyst length 71 (73) 80 µm, breadth 59 (62) 68 µm; endocyst 48 (53) 68 µm × 51 (55) 60 µm; apical horn 7 (9) 10 µm; antapical horns, left 5 (9) 13 µm, right, 0 (2) 3 µm; when present processes up to 3 µm (seven specimens).
Norwegian specimens:
Range: Pericyst length 73 (77) 87 µm, breadth 57 (65) 71 µm; endocyst 46 (57) 66 µm × 57 (64) 71 µm; apical horn 5 (7) 12 µm; antapical horns, left 3 (10) 16 µm, right 0 (4) 7 µm; when processes up to 5 µm (15 specimens).
Comparisons: The pentagonal ambital outline, the cingular flange and the presence of processes and partially developed sutural ridges distinguish O. epelidosphaeroides sp. nov. from all other Ovoidinium species. The ambital outline of this species resembles that of Yalkalpodinium scutum Morgan Citation1980, but the archaeopyle of the latter has been interpreted as type tA and its tabulation as gonyaulacoid. O. epelidosphaeroides sp. nov. differs from Ascodinium in being bicavate and having a much wider archaeopyle with a more angulose suture. O epelidosphaeroides sp. nov. resembles Epelidosphaeridia in the wide, slightly angulose archaeopyle suture, and in the shape of the short processes when these occur. It differs in having well-defined, wide pericoels, a cingular flange, and only a small number of processes. Less cavate specimens of O. epelidosphaeroides sp. nov. with more numerous processes and a less prominent cingular flange, displaying morphological similarities with Epelidosphaeridia manifesta sp. nov., are present in the assemblages from Greenland and offshore northern Norway (figures 15–16). These suggest a phyletic relation between O. epelidosphaeroides and E. manifesta sp. nov. and, by extension, between the genera Ovoidinium and Epelidosphaeridia.
Distribution: The species was first reported from the Troms and Hammerfest basins offshore north-west Norway (Costa Citation1985) and later described as Ovoidinium? sp. 2 by Nøhr-Hansen (Citation1993) from North-East Greenland.
Age: FO and LO in the Early Cenomanian. A latest late Albian to ?Early Cenomanian age was tentatively given by Nøhr-Hansen (Citation1993).
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Original description Nøhr-Hansen et al., 2017: figures 1–16; figures 10–12
Citation1993 Ovoidinium sp. 2; Nøhr-Hansen, p. 92, pl. 16, figs 5–8.
Derivation of name: ‘epelidosphaeroides’ refers to the morphological relation of this species to Epelidosphaeridia, indicated by the existence of intermediate morphotypes between both taxa.
Holotype: figure 1, GGU sample no. 522081-4 EF Z21-2.
Type locality: Section 30 of Nøhr-Hansen Citation1993 and GEUS PAL-3/2011, Tværdal, Geographical Society Ø, North-East Greenland (72°58’N, 23°02’E).
Diagnosis: A bicavate species of Ovoidinium with a pentagonal ambital outline, a short apical horn and one or two reduced antapical horns, of which the right is commonly vestigial. Cingulum marked on the dorsal face by a flange. Sulcus indicated by low ridges or folds, straight and very wide. Periphragm smooth (figures 1–12) or bearing a few short, solid sutural processes with a simple or buccinate tip. Tabulation not or only poorly expressed. Archaeopyle tAtI (1’–4’ + 1a–3a) with a wide suture which is slightly angulose on the dorsal face (, figures 2, 11; figure 11), and gently curved to symmetrically subtriangular on the ventral face.
Description: Medium-sized, dorsoventrally compressed bicavate cysts. The pericyst ambitus is subpentagonal, slightly asymmetrical. The epicyst ambitus is triangular, terminating in a short apical horn that is distally blunt and occasionally bears an apical pore. The hypocyst, commonly larger than the epicyst, is trapezoidal with a slanted antapex. The left antapical horn is broad, distally acuminate and may be reduced; the right antapical horn is reduced or absent. The endocyst ambitus is circular to elliptical. Peri- and endophragm are in contact along the central portions of the cyst but separate anteriorly and posteriorly to form pericoels of variable width. Periphragm hyaline, smooth or with faint longitudinal striations. The periphragm may bear a small number of solid, rod-like, 1–3 µm long, sutural processes with a simple, buccinate or capitate tip, and sometimes also partially developed low, sutural ridges (figures 13–16; figure 10). The endophragm is smooth.
The cingulum is marked on the dorsal side by a prominent flange, formed by a fold on the periphragm. A double row of sparse processes distributed along incomplete sutural ridges is often observable on the cyst's ventral face. The sulcus, flanked by distally smooth or denticulate ridges, is broad, straight (longitudinally aligned with the cyst central axis), and moderately indented, and occupies most of the ventral face (figure 1;, figure 10).
Archaeopyle type tAtI (1’–4’ + 1a–3a), wide. The precingular edge of the three intercalary plates is often reflected by a distinct tripartite indentation centrally located on the archaeopyle's dorsal suture, and/or a corresponding tripartite dorsal opercular margin. On the ventral face, the archaeopyle suture is generally smooth and straight or gently curved. Occasionally, a short, subtriangular, tongue-like projection, which corresponds to the posterior edge of apical plate 1’, can be seen on the ventral opercular margin. The operculum is simple, free or adherent.
Tabulation partially expressed by the cingulum, the archaeopyle suture and the distribution of the ornament when present. Nodular inclusions (omphali, or biopolymeric accumulation bodies; Evitt Citation1985), often occur on the inner ventral side of the endocyst (e.g., figures 1, 3, 13).
Dimensions
Greenland specimens:
Holotype: Pericyst length 74 µm, breadth 66 µm; endocyst, 51 µm × 51 µm; apical horn 7 µm; antapical horns, left 8 µm, right 2 µm.
Range: Pericyst length 71 (73) 80 µm, breadth 59 (62) 68 µm; endocyst 48 (53) 68 µm × 51 (55) 60 µm; apical horn 7 (9) 10 µm; antapical horns, left 5 (9) 13 µm, right, 0 (2) 3 µm; when present processes up to 3 µm (seven specimens).
Norwegian specimens:
Range: Pericyst length 73 (77) 87 µm, breadth 57 (65) 71 µm; endocyst 46 (57) 66 µm × 57 (64) 71 µm; apical horn 5 (7) 12 µm; antapical horns, left 3 (10) 16 µm, right 0 (4) 7 µm; when processes up to 5 µm (15 specimens).
Comparisons: The pentagonal ambital outline, the cingular flange and the presence of processes and partially developed sutural ridges distinguish O. epelidosphaeroides sp. nov. from all other Ovoidinium species. The ambital outline of this species resembles that of Yalkalpodinium scutum Morgan Citation1980, but the archaeopyle of the latter has been interpreted as type tA and its tabulation as gonyaulacoid. O. epelidosphaeroides sp. nov. differs from Ascodinium in being bicavate and having a much wider archaeopyle with a more angulose suture. O epelidosphaeroides sp. nov. resembles Epelidosphaeridia in the wide, slightly angulose archaeopyle suture, and in the shape of the short processes when these occur. It differs in having well-defined, wide pericoels, a cingular flange, and only a small number of processes. Less cavate specimens of O. epelidosphaeroides sp. nov. with more numerous processes and a less prominent cingular flange, displaying morphological similarities with Epelidosphaeridia manifesta sp. nov., are present in the assemblages from Greenland and offshore northern Norway (figures 15–16). These suggest a phyletic relation between O. epelidosphaeroides and E. manifesta sp. nov. and, by extension, between the genera Ovoidinium and Epelidosphaeridia.
Distribution: The species was first reported from the Troms and Hammerfest basins offshore north-west Norway (Costa Citation1985) and later described as Ovoidinium? sp. 2 by Nøhr-Hansen (Citation1993) from North-East Greenland.
Age: FO and LO in the Early Cenomanian. A latest late Albian to ?Early Cenomanian age was tentatively given by Nøhr-Hansen (Citation1993).