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Sentusidinium prolatum
Plate 31, Figures 4, 8, 12, 15
Holotype: Plate 31, Figures 15.
Paratype: Plate 31, Figure 8.
Type Locality: Well 14/19-19 at 8769.70ft (conventional core chip), early Barremian.
Holotype: Well 14/19-19 at 8769.70ft. E.F. W49.1. Paratype: Well 14/19-19 at 8792.90ft E.F. R45.2.
Derivation of Name: From the Latin prolatus, extended, elongated- in reference to the shape of this species.
Diagnosis: Aspecies of intermediate size with an elongate body and smoothly rounded to slightly pointed poles. The autophragm is fairly thick and minutely fibro-perforate, sometimes bearing very small coni; ornament is consistent over individual specimens. Loss of four apical plates leaves a zig-zag archeopyle very high on the cyst. In some specimens the operculum appears to split during archeopyle formation. Six precingular plates are indicated by the principle archeopyle suture but there is no other indication of tabulation.
Dimensions: Holotype: 89 × 63 μm.
Overall: 104 (86) 78 μm × 81 (68) 58 μm
Specimens Measured: 20
Remarks: The fairly large size, elongate shape and very high position of the small archeopyle characterise this species. Similarly elongate species were described as Batiacasphaera ovata Backhouse 1987 and Batiacasphaera subtilis Stover and Helby 1987b, which were combined as B. subtilis by Wood et al. (op. cit., p. 69).
Although the surface of the autophragm in B. subtilis, as originally described by Stover and Helby (1987b, p. 226) is, “smooth, chagrenate, finely granular, or with low, ill-defined, irregularly shaped projections”, several of their illustrations in Figs. 2 and 3 appear to show reticulate to rugulate ornamentation, and it therefore possesses a stated criterion for Batiacasphaera in Wood et al. (op. cit.). However, B ovata does not, being described as finely granular by Backhouse (op. cit., p. 215). Both B. ovata and B. subtilis are much smaller than Sentusidinium prolatum n. sp. with a relatively wider archeopyle, and with the autophragm thinning towards the poles, a feature not observed in S. prolatum.
Sentusidinium prolatum n. sp. ranged between 8829.00 ft and 8742.50 ft in well 14/19-19, latest Hauterivian to early Barremian, palynofloral Subzones LKP16.2 to LKP17.1, although it was common only between 8792.90 ft and 8742.50 ft, coinciding with the acme of Batiacasphaera variabilis Duxbury n. sp. Only a single specimen of Sentusidinium prolatum was recorded in well 14/19-21, at 10295.50 ft (palynofloral Subzone LKP17.1), and this again coincided with an influx (abundant) of B. variabilis.
Holotype: Plate 31, Figures 15.
Paratype: Plate 31, Figure 8.
Type Locality: Well 14/19-19 at 8769.70ft (conventional core chip), early Barremian.
Holotype: Well 14/19-19 at 8769.70ft. E.F. W49.1. Paratype: Well 14/19-19 at 8792.90ft E.F. R45.2.
Derivation of Name: From the Latin prolatus, extended, elongated- in reference to the shape of this species.
Diagnosis: Aspecies of intermediate size with an elongate body and smoothly rounded to slightly pointed poles. The autophragm is fairly thick and minutely fibro-perforate, sometimes bearing very small coni; ornament is consistent over individual specimens. Loss of four apical plates leaves a zig-zag archeopyle very high on the cyst. In some specimens the operculum appears to split during archeopyle formation. Six precingular plates are indicated by the principle archeopyle suture but there is no other indication of tabulation.
Dimensions: Holotype: 89 × 63 μm.
Overall: 104 (86) 78 μm × 81 (68) 58 μm
Specimens Measured: 20
Remarks: The fairly large size, elongate shape and very high position of the small archeopyle characterise this species. Similarly elongate species were described as Batiacasphaera ovata Backhouse 1987 and Batiacasphaera subtilis Stover and Helby 1987b, which were combined as B. subtilis by Wood et al. (op. cit., p. 69).
Although the surface of the autophragm in B. subtilis, as originally described by Stover and Helby (1987b, p. 226) is, “smooth, chagrenate, finely granular, or with low, ill-defined, irregularly shaped projections”, several of their illustrations in Figs. 2 and 3 appear to show reticulate to rugulate ornamentation, and it therefore possesses a stated criterion for Batiacasphaera in Wood et al. (op. cit.). However, B ovata does not, being described as finely granular by Backhouse (op. cit., p. 215). Both B. ovata and B. subtilis are much smaller than Sentusidinium prolatum n. sp. with a relatively wider archeopyle, and with the autophragm thinning towards the poles, a feature not observed in S. prolatum.
Sentusidinium prolatum n. sp. ranged between 8829.00 ft and 8742.50 ft in well 14/19-19, latest Hauterivian to early Barremian, palynofloral Subzones LKP16.2 to LKP17.1, although it was common only between 8792.90 ft and 8742.50 ft, coinciding with the acme of Batiacasphaera variabilis Duxbury n. sp. Only a single specimen of Sentusidinium prolatum was recorded in well 14/19-21, at 10295.50 ft (palynofloral Subzone LKP17.1), and this again coincided with an influx (abundant) of B. variabilis.