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Sindridinium anaanae
From Fensome et al., 2019:
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Original description Nøhr-Hansen, 2017:
Sindridinium anaanae gen. et sp. nov. figures 1–16; figures 1–9
1993 Ovoidinium? sp. 1; Nøhr-Hansen, p. 91, pl. 24, figs 7–10, 12, 13.
2012 Ovoidinium sp. 1; Nøhr-Hansen, pl. 1, figs 14, 15.
Derivation of name: Greenlandic ‘anaana’ for mother.
Holotype: figure 1, GGU sample no. 518602-7 EF M32-1.
Type locality: Section JHOV-2/2009, Snertadal, north Hold with Hope, North-East Greenland (73°52.122′N, 20°37.993'W).
Description: Double-walled hypocavate cysts, dorsoventral compression moderate. Pericyst ambitus slightly elongate, endocyst ambitus oval to subcircular. Periphragm and endophragm are in close contact over apical and central portions of the cyst, separating posteriorly to form a narrow hypocystal pericoel. The pericyst's antapex is rounded (e.g., figure 11) to weakly lobate (e.g. , figure 1). Apical horn absent or vestigial, cyst apex rounded or slightly angulose. Endophragm thin (< 1 µm), periphragm normally thicker (> 1 µm), smooth or bearing scattered non tabular grana, verrucae or disc-like tubercles; the density of the ornament varies on different individuals from almost none (e.g. , figures 3, 4) to almost covering the entire periphragm (e.g. , figures 8, 9). In poorly preserved specimens where the periphragm (and pericoel) may be absent, the shape of the endocyst can be used to distinguish the subcircular S. anaanae gen. et sp. nov. from the ovoid to elongate S. borealis gen. et sp. nov. (, figure 12). On some specimens, the periphragm has been affected by microbial activity (, figures 12, 13). One or two large nodular inclusions and a variable number of smaller ones, which may correspond to an omphalus, occasionally occur on the inner side of the endocyst (e.g. , figures 13, 15). Tabulation not expressed. Cingulum not evident. Sulcus frequently seen as a centrally placed, straight, longitudinal depression on the ventral face, which may be partially flanked by folds on the periphragm. Archaeopyle presumed to be type tAtI (see discussion above). The archaeopyle suture is weakly angulose and relatively narrow. Dorsally, when well preserved, it is straight to subrectangular or, rarely, slightly angulose; ventrally, the archaeopyle suture is slightly narrower, weakly curved, rarely subtriangular, with a bilaterally symmetrical outline. A small separation between peri- and endophragm may be observable along the archaeopyle margins. The operculum is free or adherent, with a rounded subpolygonal (subpentagonal) outline.
Specimens with a lobate antapex tend to have a more pointed apex (, figures 1–4), whereas the less common egg-shaped specimens have a more rounded apex (figures 8, 9) as on S. borealis gen. et sp. nov.
Dimensions
Greenland specimens:
Holotype: Pericyst length 63 µm × breadth 55 µm, endocyst length 54 µm, width of archaeopyle 33 µm.
Range: Cysts with operculum in situ: Pericyst length 53 (62) 68 µm × breadth 44 (53) 56 µm; endocyst length 48 (54) 60 µm, width of archaeopyle 26 (28) 31 µm (11 specimens).
Cysts without operculum: Pericyst 44 (54) 58 µm × breadth 44 (52) 58 µm; endocyst length 39 (46) 50 µm, width of archaeopyle 25 (30) 35 µm (11 specimens).
Norwegian specimens:
Range: Pericyst 52 (58) 69 µm × breadth 47 (54) 59 µm; endocyst 43 (50) 59 µm (14 specimens).
Distribution: The species was first reported from the Troms and Hammerfest basins, offshore north-west Norway (Costa Citation1985) and later described as Ovoidinium? sp. 1 from North-East Greenland (Nøhr-Hansen Citation1993). Recently Ovoidinium? sp. 1 has been recorded from the Kangerlussuaq Basin, southern East Greenland (Nøhr-Hansen Citation2012). The present study indicates that common Sindridinium borealis gen. et sp. nov. and S. anaanae gen. et sp. nov. may be stratigraphically separated in onshore samples from North-East Greenland. Evidence from sidewall cores taken in Norwegian Sea wells indicates that Sindridinium borealis gen. et sp. nov. coexists with S. anaanae, but becomes generally rare in the upper part of its range, where S. anaanae gen. et sp. nov. is numerically prominent. Sindridinium borealis gen. et sp. nov. seems to be an older possible precursor for S. anaanae gen. et sp. nov. Sindridinium anaanae gen. et sp. nov. has its FO just above the last common occurrence of the S. borealis gen. et sp. nov. at the east of Fosdalen section Hold with Hope. Sindridinium anaanae gen. et sp. nov. was not recorded in the Trunch Borehole in the five palynologically productive samples above the LO of S. borealis gen. et sp. nov. Unfortunately, due to a conspicuous barren interval that extends from the middle Cenomanian to the upper Turonian section, it is not known whether the species exists in the area. Additional studies are required to test the southern limit of S. anaanae gen. et sp. nov.
Age: A late Albian to ?Early Cenomanian age has been reported by Nøhr-Hansen (Citation1993, Citation2012). The present study indicates an FO in the Lower Cenomanian; the uppermost limit of the species range is not believed to have been observed in this study, but most likely occurs in the Lower Cenomanian. Unpublished data from wells in the Barents Sea and Norwegian Sea indicate a Lower Cenomanian LO in offshore NW Norway.
Comparisons: The closest described forms are Ovoidinium implanum, O. scabrosum and O. verrucosum ssp. ostium, but these are normally represented by double-walled cysts with an apical horn and apical pericoel and usually have a distinct cingulum and a wider archaeopyle, and the outline of the intercalary plates is better defined on the archaeopyle suture.
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Original description Nøhr-Hansen, 2017:
Sindridinium anaanae gen. et sp. nov. figures 1–16; figures 1–9
1993 Ovoidinium? sp. 1; Nøhr-Hansen, p. 91, pl. 24, figs 7–10, 12, 13.
2012 Ovoidinium sp. 1; Nøhr-Hansen, pl. 1, figs 14, 15.
Derivation of name: Greenlandic ‘anaana’ for mother.
Holotype: figure 1, GGU sample no. 518602-7 EF M32-1.
Type locality: Section JHOV-2/2009, Snertadal, north Hold with Hope, North-East Greenland (73°52.122′N, 20°37.993'W).
Description: Double-walled hypocavate cysts, dorsoventral compression moderate. Pericyst ambitus slightly elongate, endocyst ambitus oval to subcircular. Periphragm and endophragm are in close contact over apical and central portions of the cyst, separating posteriorly to form a narrow hypocystal pericoel. The pericyst's antapex is rounded (e.g., figure 11) to weakly lobate (e.g. , figure 1). Apical horn absent or vestigial, cyst apex rounded or slightly angulose. Endophragm thin (< 1 µm), periphragm normally thicker (> 1 µm), smooth or bearing scattered non tabular grana, verrucae or disc-like tubercles; the density of the ornament varies on different individuals from almost none (e.g. , figures 3, 4) to almost covering the entire periphragm (e.g. , figures 8, 9). In poorly preserved specimens where the periphragm (and pericoel) may be absent, the shape of the endocyst can be used to distinguish the subcircular S. anaanae gen. et sp. nov. from the ovoid to elongate S. borealis gen. et sp. nov. (, figure 12). On some specimens, the periphragm has been affected by microbial activity (, figures 12, 13). One or two large nodular inclusions and a variable number of smaller ones, which may correspond to an omphalus, occasionally occur on the inner side of the endocyst (e.g. , figures 13, 15). Tabulation not expressed. Cingulum not evident. Sulcus frequently seen as a centrally placed, straight, longitudinal depression on the ventral face, which may be partially flanked by folds on the periphragm. Archaeopyle presumed to be type tAtI (see discussion above). The archaeopyle suture is weakly angulose and relatively narrow. Dorsally, when well preserved, it is straight to subrectangular or, rarely, slightly angulose; ventrally, the archaeopyle suture is slightly narrower, weakly curved, rarely subtriangular, with a bilaterally symmetrical outline. A small separation between peri- and endophragm may be observable along the archaeopyle margins. The operculum is free or adherent, with a rounded subpolygonal (subpentagonal) outline.
Specimens with a lobate antapex tend to have a more pointed apex (, figures 1–4), whereas the less common egg-shaped specimens have a more rounded apex (figures 8, 9) as on S. borealis gen. et sp. nov.
Dimensions
Greenland specimens:
Holotype: Pericyst length 63 µm × breadth 55 µm, endocyst length 54 µm, width of archaeopyle 33 µm.
Range: Cysts with operculum in situ: Pericyst length 53 (62) 68 µm × breadth 44 (53) 56 µm; endocyst length 48 (54) 60 µm, width of archaeopyle 26 (28) 31 µm (11 specimens).
Cysts without operculum: Pericyst 44 (54) 58 µm × breadth 44 (52) 58 µm; endocyst length 39 (46) 50 µm, width of archaeopyle 25 (30) 35 µm (11 specimens).
Norwegian specimens:
Range: Pericyst 52 (58) 69 µm × breadth 47 (54) 59 µm; endocyst 43 (50) 59 µm (14 specimens).
Distribution: The species was first reported from the Troms and Hammerfest basins, offshore north-west Norway (Costa Citation1985) and later described as Ovoidinium? sp. 1 from North-East Greenland (Nøhr-Hansen Citation1993). Recently Ovoidinium? sp. 1 has been recorded from the Kangerlussuaq Basin, southern East Greenland (Nøhr-Hansen Citation2012). The present study indicates that common Sindridinium borealis gen. et sp. nov. and S. anaanae gen. et sp. nov. may be stratigraphically separated in onshore samples from North-East Greenland. Evidence from sidewall cores taken in Norwegian Sea wells indicates that Sindridinium borealis gen. et sp. nov. coexists with S. anaanae, but becomes generally rare in the upper part of its range, where S. anaanae gen. et sp. nov. is numerically prominent. Sindridinium borealis gen. et sp. nov. seems to be an older possible precursor for S. anaanae gen. et sp. nov. Sindridinium anaanae gen. et sp. nov. has its FO just above the last common occurrence of the S. borealis gen. et sp. nov. at the east of Fosdalen section Hold with Hope. Sindridinium anaanae gen. et sp. nov. was not recorded in the Trunch Borehole in the five palynologically productive samples above the LO of S. borealis gen. et sp. nov. Unfortunately, due to a conspicuous barren interval that extends from the middle Cenomanian to the upper Turonian section, it is not known whether the species exists in the area. Additional studies are required to test the southern limit of S. anaanae gen. et sp. nov.
Age: A late Albian to ?Early Cenomanian age has been reported by Nøhr-Hansen (Citation1993, Citation2012). The present study indicates an FO in the Lower Cenomanian; the uppermost limit of the species range is not believed to have been observed in this study, but most likely occurs in the Lower Cenomanian. Unpublished data from wells in the Barents Sea and Norwegian Sea indicate a Lower Cenomanian LO in offshore NW Norway.
Comparisons: The closest described forms are Ovoidinium implanum, O. scabrosum and O. verrucosum ssp. ostium, but these are normally represented by double-walled cysts with an apical horn and apical pericoel and usually have a distinct cingulum and a wider archaeopyle, and the outline of the intercalary plates is better defined on the archaeopyle suture.