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Vexillocysta spinosa
From Fensome et al., 2019:
Vexillocysta spinosa Duxbury, 2018, p.196–197, pl.3, figs.9,13–15.
Holotype: Duxbury, 2018, pl.3, fig.9.
Age: late Berriasian.
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Original description: [Duxbury, 2018]:
Vexillocysta spinosa Duxbury n. sp.
Plate 3, figures 9, 13–15
Holotype: Plate 3, Figure 9.
Type Locality: Well 20/01-10Z at 9142.30ft (conventional core chip), upper Berriasian. Holotype: E.F. V29.2.
Derivation of Name: From the Latin spinosus, thorny, in reference to the ornament of this species.
Diagnosis: An ellipsoidal dinocyst bearing penitabular ridges or low crests ornamented with fairly long, flat, distally capitate spines. Spine bases are broad and tend to coalesce, producing an undulating distal edge to each crest. The archeopyle is tetratabular apical, with the operculum usually fully detached, and six precingular plates are indicated by the archeopyle margin.
Dimensions: Holotype (operculum detached): Central body – 46 × 41 µm.
Overall: 68 × 68 µm.
All measured specimens (operculum detached): Central body – 51 (42) 35 µm × 46 (38) 33 µm.
Overall: 68 (60) 51 µm × 68 (56) 46 µm.
Specimens Measured: 22.
Remarks: Despite its common occurrence throughout much of its range, the complexity of crests and the large number of spines in this species have prevented a full assessment of its tabulation. The operculum is almost invariably lost, but rare specimens (Plate 3, Figure 15) indicate a tetratabular apical series and the archeopyle margin suggests six precingular plates.
Vexillocysta spinosa n. sp. shares several features with Vexillocysta colligata (Morgan 1980) n. comb. including the presence of penitabular crests bearing flat spines and a tetratabular apical archeopyle. It differs, however in being distinctly elongate and thicker-walled, and in having higher crests and significantly fewer, more robust spines.
In overall morphology this species displays several characteristics in common with Epiplosphaera Klement 1960, but without the surface reticulum typical of Epiplosphaera bireticulata Klement 1960, the type species and E. reticulospinosa Klement 1960.
Vexillocysta spinosa n. sp. ranges from the base of the studied section at Speeton as high as Bed D4C (Berriasian to early Valanginian), with its peak at the top of the Berriasian, upper Bed D5. As it is also a common component of sections of this age offshore, this species is particularly valuable in well correlations, and its peak is a useful top Berriasian marker.
Vexillocysta spinosa Duxbury, 2018, p.196–197, pl.3, figs.9,13–15.
Holotype: Duxbury, 2018, pl.3, fig.9.
Age: late Berriasian.
---------------------------------------------------------------------------------------------------
Original description: [Duxbury, 2018]:
Vexillocysta spinosa Duxbury n. sp.
Plate 3, figures 9, 13–15
Holotype: Plate 3, Figure 9.
Type Locality: Well 20/01-10Z at 9142.30ft (conventional core chip), upper Berriasian. Holotype: E.F. V29.2.
Derivation of Name: From the Latin spinosus, thorny, in reference to the ornament of this species.
Diagnosis: An ellipsoidal dinocyst bearing penitabular ridges or low crests ornamented with fairly long, flat, distally capitate spines. Spine bases are broad and tend to coalesce, producing an undulating distal edge to each crest. The archeopyle is tetratabular apical, with the operculum usually fully detached, and six precingular plates are indicated by the archeopyle margin.
Dimensions: Holotype (operculum detached): Central body – 46 × 41 µm.
Overall: 68 × 68 µm.
All measured specimens (operculum detached): Central body – 51 (42) 35 µm × 46 (38) 33 µm.
Overall: 68 (60) 51 µm × 68 (56) 46 µm.
Specimens Measured: 22.
Remarks: Despite its common occurrence throughout much of its range, the complexity of crests and the large number of spines in this species have prevented a full assessment of its tabulation. The operculum is almost invariably lost, but rare specimens (Plate 3, Figure 15) indicate a tetratabular apical series and the archeopyle margin suggests six precingular plates.
Vexillocysta spinosa n. sp. shares several features with Vexillocysta colligata (Morgan 1980) n. comb. including the presence of penitabular crests bearing flat spines and a tetratabular apical archeopyle. It differs, however in being distinctly elongate and thicker-walled, and in having higher crests and significantly fewer, more robust spines.
In overall morphology this species displays several characteristics in common with Epiplosphaera Klement 1960, but without the surface reticulum typical of Epiplosphaera bireticulata Klement 1960, the type species and E. reticulospinosa Klement 1960.
Vexillocysta spinosa n. sp. ranges from the base of the studied section at Speeton as high as Bed D4C (Berriasian to early Valanginian), with its peak at the top of the Berriasian, upper Bed D5. As it is also a common component of sections of this age offshore, this species is particularly valuable in well correlations, and its peak is a useful top Berriasian marker.