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Fentonia bjaerkei
Fentonia bjaerkei (Smelror, 1987) emend. Bailey and Hogg, 1995
Acritarch genus.
NOW Limbicysta (acritarch). Originally Parvocysta, subsequently Fentonia, thirdly (and now) Limbicysta (acritarch), fourthly Neofentonia (generic name illegitimate; acritarch).
Holotype: Smelror, 1987, fig.4G
Locus typicus: Franz Josef Land, Arctic
Stratum typicum: Late Callovian
1980 Parvocysta? sp. B: Bjaerke, p. 68-69, pl. 1, figs 13, 16, 17, text fig. 3E.
1984 Parvocysta cf. barbata Bjaerke 1980: Riding, pl. 1, fig.8.
1984 Parvocysta cf. barbata Bjaerke 1980: Riding, pl. 6, fig. L
1987 Parvocysta bjaerkei: Smelror, p. 227, 230, fig. 4G.
Amended description: Bailey and Hogg, 1995, p. 58
Small, with strong dorsoventral compression autophragm and conspicuous protrusions. Apical protrusion moderately rounded. Longitudinal folds may be developed in the apical region. Lateral protrusions terminate in three to five smaller acute protrusions which themselves may be distally bifurcate. Antapex flat or mildly concave. No excystment aperture observed. Autophragm more or less smooth.
Affinities: Bailey and Hogg, 1995, p. 58
Some other genera, eg. Subtilisphaera, Palaeohystrichophora also do not have obvious archaeopyles and are still considered to be dinoflagellate cysts. These have additional features, such as a paracingulum and parasulcus.
Stratigraphic distribution: Bailey and Hogg, 1995, p. 58
This taxon is recorded consistently in sediments of Late Pliensbachian to Early Bathonian age in northwest Europe (pers. obs.). Younger records from the Late Bathonian and Callovian (eg. Bjaerke, 1977; Smelror, 1987) are very inconsistent and are considered to be reworked.
Acritarch genus.
NOW Limbicysta (acritarch). Originally Parvocysta, subsequently Fentonia, thirdly (and now) Limbicysta (acritarch), fourthly Neofentonia (generic name illegitimate; acritarch).
Holotype: Smelror, 1987, fig.4G
Locus typicus: Franz Josef Land, Arctic
Stratum typicum: Late Callovian
1980 Parvocysta? sp. B: Bjaerke, p. 68-69, pl. 1, figs 13, 16, 17, text fig. 3E.
1984 Parvocysta cf. barbata Bjaerke 1980: Riding, pl. 1, fig.8.
1984 Parvocysta cf. barbata Bjaerke 1980: Riding, pl. 6, fig. L
1987 Parvocysta bjaerkei: Smelror, p. 227, 230, fig. 4G.
Amended description: Bailey and Hogg, 1995, p. 58
Small, with strong dorsoventral compression autophragm and conspicuous protrusions. Apical protrusion moderately rounded. Longitudinal folds may be developed in the apical region. Lateral protrusions terminate in three to five smaller acute protrusions which themselves may be distally bifurcate. Antapex flat or mildly concave. No excystment aperture observed. Autophragm more or less smooth.
Affinities: Bailey and Hogg, 1995, p. 58
Some other genera, eg. Subtilisphaera, Palaeohystrichophora also do not have obvious archaeopyles and are still considered to be dinoflagellate cysts. These have additional features, such as a paracingulum and parasulcus.
Stratigraphic distribution: Bailey and Hogg, 1995, p. 58
This taxon is recorded consistently in sediments of Late Pliensbachian to Early Bathonian age in northwest Europe (pers. obs.). Younger records from the Late Bathonian and Callovian (eg. Bjaerke, 1977; Smelror, 1987) are very inconsistent and are considered to be reworked.