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Nidarocysta jubilaea
Nidarocysta *jubilaea Monteil, 1997, p.394, pl.1, figs.1–6; pl.2, figs.1–6; pl.3, figs.1–3; pl.4, figs.1–6; pl.5, figs.1–6; pl.6, figs.1–6; pl.7, figs.1–6; pl.8, figs.1–6; text-figs.3a–f,4A–D,5A–D,6a–f,7a–f,8a–b.
Holotype: Monteil, 1997, pl.3, fig.3; pl.4, figs.1–6; text-figs.6a–b.
Age: latest Oxfordian–earliest Kimmeridgian.
Orginal description (Monteil, 1997)
Type-locality IKU core 82-5 (65° 38' 38.1" N; 10° 56' 32.7" E), Offshore MidNorway, Tremdelag Platform, northeastern Froan Basin.
Type-strata Depth 16.95 m below top of the core, latest Oxfordian to earliest Kimmeridgian (transitional beds between the Rosenkrantzi to Baylei Ammonite zones).
Diagnosis : same as for the genus, with the exception that the formula paratabulation is defined as follows: 2pr, ? 0-1 a, 4', 6", 6c, 6"', 1 p, 1 "", 3-?5s, and the ornamentation is defined as scab rate to minutely granulate.
Diagnosis for genus: Diagnosis
Shape. Biconical with a pointed apex and a rounded antapex.
Wall relationships. Autophragm only, fragile, thin and transparent.
Wall features. Parasutural thread-like pattern, typically locally separated from the cyst wall; surface ornamentation psilate to scabrate, or minutely granulate.
Archeopyle. Precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by partial random splitting (rs) around 3" margin and, sometimes, adjacent paraplates; adnate operculum (3").
Paratabulation. Clearly indicated by parasutural thread-like structures; gonyaulacacean, formula: 2pr, 0-1a, 4', 6", 6c, 6'",1p, 1"", 3-?5s.
Paracingulum. Indicated by six rectangular transversely elongate paraplates; laevorotatory.
Parasulcus. Clearly indicated and subdivided, rs and Is boundary excepted.
Size. Small to intermediate; about 45 μm to 55 μm in diameter and 50 μm to 65 μm in length.
Remarks
Where visible, the apical areas of all specimens of Nidarocysta jubi/aea gen. et sp. nov. have one small dorsal intercalary paraplate. However, in order not to overly restrict the definition of this new monospecific genus, I prefer to include within its diagnosis the variability 0-1 a. Additionally, specimens lacking a dorsal intercalary paraplate, i.e. ?0-1 a, are questionably included in the type species diagnosis. In the same sense, the generic diagnosis is broadened to include ornamental variation psilate to minutely granulate, although only scabrate to minutely granulate ornamentation was observed. The presence of a boundary between the two paraplates rs and Is could be not clearly demonstrated (Pl. 6, fig. 1; Fig. 6e).
Dimensions Length range: 50 μm-65 μm; diameter range: 44 μm-55 μm; 20 specimens measured.
Stratigraphical and geographical distributionIn Mid-Norway, Nidarocysta jubilaea gen. et sp. nov. is reported
as occupying a very restricted stratigraphic interval, ranging from the Rosenkrantzi to Baylei Ammonite zones (latest
Oxfordian to earliest Kimmeridgian). In the IKU Core 82-5,however, sediments of latest Oxfordian age (Rosenkrantzi Ammonite zone) apparently immediately overlie the Middle Oxfordian section (Tenuiserratum-Densiplicatum ammonite zones), and possibly occurrences of this new taxon in one or more of the Regulare, Serratum or Glosense
Ammonite zones (Late Oxfordian) may be recorded in the future. In Greenland, this new taxon is also reported from an interval of undifferentiated Rosenkrantzi to Baylei equivalent-Ammonite zone sediments. Nidarocysta jubilaea gen. et sp. nov. occurs also in the same interval in England, the British North Sea, the North Viking Graben, the
Danish Graben and the Danish North Sea (IKU internal data). The present known geographical distribution of Nidarocysta gen. nov. is summarised in Figure 9.
Remarks In IKU Core 82-5, Exiguisphaera cf. phragma sensu THOMAS & Cox 1988 and Nidarocysta jubilaea gen.
et sp. nov. have exactly the same stratigraphic range. THOMAS & Cox (1988) reported E. cf. phragma from the Rosenkrantzi to Baylei Ammonite Zones, with an isolated occurrence in the Serratum Zone, in the Hamme borehole (North Yorkshire, England). E. cf. phragma sensu THOMAS & Cox 1988 could be also a useful marker for this interval offshore Mid-Norway.
Holotype: Monteil, 1997, pl.3, fig.3; pl.4, figs.1–6; text-figs.6a–b.
Age: latest Oxfordian–earliest Kimmeridgian.
Orginal description (Monteil, 1997)
Type-locality IKU core 82-5 (65° 38' 38.1" N; 10° 56' 32.7" E), Offshore MidNorway, Tremdelag Platform, northeastern Froan Basin.
Type-strata Depth 16.95 m below top of the core, latest Oxfordian to earliest Kimmeridgian (transitional beds between the Rosenkrantzi to Baylei Ammonite zones).
Diagnosis : same as for the genus, with the exception that the formula paratabulation is defined as follows: 2pr, ? 0-1 a, 4', 6", 6c, 6"', 1 p, 1 "", 3-?5s, and the ornamentation is defined as scab rate to minutely granulate.
Diagnosis for genus: Diagnosis
Shape. Biconical with a pointed apex and a rounded antapex.
Wall relationships. Autophragm only, fragile, thin and transparent.
Wall features. Parasutural thread-like pattern, typically locally separated from the cyst wall; surface ornamentation psilate to scabrate, or minutely granulate.
Archeopyle. Precingular archeopyle, type (P)rsa, with an unusual opening mode; archeopyle not developed or only expressed by partial random splitting (rs) around 3" margin and, sometimes, adjacent paraplates; adnate operculum (3").
Paratabulation. Clearly indicated by parasutural thread-like structures; gonyaulacacean, formula: 2pr, 0-1a, 4', 6", 6c, 6'",1p, 1"", 3-?5s.
Paracingulum. Indicated by six rectangular transversely elongate paraplates; laevorotatory.
Parasulcus. Clearly indicated and subdivided, rs and Is boundary excepted.
Size. Small to intermediate; about 45 μm to 55 μm in diameter and 50 μm to 65 μm in length.
Remarks
Where visible, the apical areas of all specimens of Nidarocysta jubi/aea gen. et sp. nov. have one small dorsal intercalary paraplate. However, in order not to overly restrict the definition of this new monospecific genus, I prefer to include within its diagnosis the variability 0-1 a. Additionally, specimens lacking a dorsal intercalary paraplate, i.e. ?0-1 a, are questionably included in the type species diagnosis. In the same sense, the generic diagnosis is broadened to include ornamental variation psilate to minutely granulate, although only scabrate to minutely granulate ornamentation was observed. The presence of a boundary between the two paraplates rs and Is could be not clearly demonstrated (Pl. 6, fig. 1; Fig. 6e).
Dimensions Length range: 50 μm-65 μm; diameter range: 44 μm-55 μm; 20 specimens measured.
Stratigraphical and geographical distributionIn Mid-Norway, Nidarocysta jubilaea gen. et sp. nov. is reported
as occupying a very restricted stratigraphic interval, ranging from the Rosenkrantzi to Baylei Ammonite zones (latest
Oxfordian to earliest Kimmeridgian). In the IKU Core 82-5,however, sediments of latest Oxfordian age (Rosenkrantzi Ammonite zone) apparently immediately overlie the Middle Oxfordian section (Tenuiserratum-Densiplicatum ammonite zones), and possibly occurrences of this new taxon in one or more of the Regulare, Serratum or Glosense
Ammonite zones (Late Oxfordian) may be recorded in the future. In Greenland, this new taxon is also reported from an interval of undifferentiated Rosenkrantzi to Baylei equivalent-Ammonite zone sediments. Nidarocysta jubilaea gen. et sp. nov. occurs also in the same interval in England, the British North Sea, the North Viking Graben, the
Danish Graben and the Danish North Sea (IKU internal data). The present known geographical distribution of Nidarocysta gen. nov. is summarised in Figure 9.
Remarks In IKU Core 82-5, Exiguisphaera cf. phragma sensu THOMAS & Cox 1988 and Nidarocysta jubilaea gen.
et sp. nov. have exactly the same stratigraphic range. THOMAS & Cox (1988) reported E. cf. phragma from the Rosenkrantzi to Baylei Ammonite Zones, with an isolated occurrence in the Serratum Zone, in the Hamme borehole (North Yorkshire, England). E. cf. phragma sensu THOMAS & Cox 1988 could be also a useful marker for this interval offshore Mid-Norway.