Back
Batioladinium mucronatum
Plate 6, Figures 17, 21
Batioladinium shaftesburiensis sensu Nøhr-Hansen in ÅRHUS et al. 1990, fig. 11, G and H
Holotype: Plate 6, Figure 17
Type Locality: early Barremian, Speeton Clay Formation, Speeton. Holotype: Slide topLB4D/2, E.F. T46.0.
Derivation of Name: From the Latin mucronatus, pointed - in reference to the sharply-pointed antapical horns of this species.
Diagnosis: A smooth to very finely granular, elongate pareodinioid dinocyst with a long, sharply-tapering apical horn. The antapex is strongly concave and produced into two fairly long antapical horns which are of equal length. The antapical horns are relatively broad proximally, constrict sharply at about half their length and then taper to a sharp point. The distal half of the antapical horns is solid. The archeopyle is apical, leaving a deep sulcal notch on opercular detachment.
Dimensions: Holotype (complete): Length - 137 μm. Width - 38 μm
Antapical horns: 20 μm
Overall (operculum detached): 106 (90) 71 μm × 43 (37) 33 μm
Antapical horns: 23 (20) 18 μm
Specimens Measured: 5
Remarks: The antapical horns of this species are its main distinguishing feature. In possessing a markedly concave antapex, Batioladinium mucronatum is similar to Batioladinium jaegeri (Alberti 1961) Brideaux 1975 and B. longicornutum (Alberti 1961) Brideaux 1975 but it differs in possessing antapical horns intermediate in length to both. In addition, B. jaegeri has a typical “fish-tail” antapex, where the hollow horns are part of the cyst capsule. This contrasts to the horns of B. longicornutum and B. mucronatum which are partly hollow and partly solid extensions. The significantly greater length of antapical horns in B. longicornutum, their tendancy to have irregular, ragged surface ornament and the thicker test wall of that species distinguish it from B. mucronatum.
Batioladinium mucronatum also resembles Batioladinium shaftesburiense Nøhr-Hansen 1993, which differs in possessing longer horns (especially the apical), a more delicate test and antapical horns which appear to be completely hollow and gradually tapering, as opposed to the partly hollow horns of B. mucronatum which constrict sharply at about half their length.
In describing Batioladinium shaftesburiense, Nøhr-Hansen (1993, p. 46, 47) included specimens assigned to “Batioladinium shaftesburiensis sensu Nøhr-Hansen” in Århus et al. (1990, Fig. 11, G and H). These were from Barents Sea well 7320/3-U-1 at 20.94m (early Barremian) and 28.94 m (early Barremian to Hauterivian), and Århus et al. (1990, p. 170, 171) remarked that in that well, samples as deep as 27.44 m yielded Tenua anaphrissa, which “favours a late Early Barremian dating”. Specimens illustrated in Århus et al. (1990, Fig. 11, G and H) are included in Batioladinium mucronatum here as these clearly show the characteristic antapical horns described above.
Nøhr-Hansen (1993, p. 47) recognised that, “Apart from the lower Barremian occurrence in the Barents Sea, the species (B. shaftesburiense) seems to be restricted to the Albian”. An Albian FAD for B. shaftesburiense was further confirmed in Nøhr-Hansen et al. (2019, p. 24, 25), where it was described “in the middle part” of Subzone Litosphaeridium arundum (1) of Nøhr-Hansen (1993), middle Albian.
The observed range of Batioladinium mucronatum at Speeton was between Beds LB6 and LB2D (early Barremian, top variabilis to fissicostatum Zones), and the FAD of Tenua anaphrissa was immediately above this range, in Bed LB1, suggesting a very similar range for B. mucronatum to that observed by Århus et al. (op. cit.).
Batioladinium shaftesburiensis sensu Nøhr-Hansen in ÅRHUS et al. 1990, fig. 11, G and H
Holotype: Plate 6, Figure 17
Type Locality: early Barremian, Speeton Clay Formation, Speeton. Holotype: Slide topLB4D/2, E.F. T46.0.
Derivation of Name: From the Latin mucronatus, pointed - in reference to the sharply-pointed antapical horns of this species.
Diagnosis: A smooth to very finely granular, elongate pareodinioid dinocyst with a long, sharply-tapering apical horn. The antapex is strongly concave and produced into two fairly long antapical horns which are of equal length. The antapical horns are relatively broad proximally, constrict sharply at about half their length and then taper to a sharp point. The distal half of the antapical horns is solid. The archeopyle is apical, leaving a deep sulcal notch on opercular detachment.
Dimensions: Holotype (complete): Length - 137 μm. Width - 38 μm
Antapical horns: 20 μm
Overall (operculum detached): 106 (90) 71 μm × 43 (37) 33 μm
Antapical horns: 23 (20) 18 μm
Specimens Measured: 5
Remarks: The antapical horns of this species are its main distinguishing feature. In possessing a markedly concave antapex, Batioladinium mucronatum is similar to Batioladinium jaegeri (Alberti 1961) Brideaux 1975 and B. longicornutum (Alberti 1961) Brideaux 1975 but it differs in possessing antapical horns intermediate in length to both. In addition, B. jaegeri has a typical “fish-tail” antapex, where the hollow horns are part of the cyst capsule. This contrasts to the horns of B. longicornutum and B. mucronatum which are partly hollow and partly solid extensions. The significantly greater length of antapical horns in B. longicornutum, their tendancy to have irregular, ragged surface ornament and the thicker test wall of that species distinguish it from B. mucronatum.
Batioladinium mucronatum also resembles Batioladinium shaftesburiense Nøhr-Hansen 1993, which differs in possessing longer horns (especially the apical), a more delicate test and antapical horns which appear to be completely hollow and gradually tapering, as opposed to the partly hollow horns of B. mucronatum which constrict sharply at about half their length.
In describing Batioladinium shaftesburiense, Nøhr-Hansen (1993, p. 46, 47) included specimens assigned to “Batioladinium shaftesburiensis sensu Nøhr-Hansen” in Århus et al. (1990, Fig. 11, G and H). These were from Barents Sea well 7320/3-U-1 at 20.94m (early Barremian) and 28.94 m (early Barremian to Hauterivian), and Århus et al. (1990, p. 170, 171) remarked that in that well, samples as deep as 27.44 m yielded Tenua anaphrissa, which “favours a late Early Barremian dating”. Specimens illustrated in Århus et al. (1990, Fig. 11, G and H) are included in Batioladinium mucronatum here as these clearly show the characteristic antapical horns described above.
Nøhr-Hansen (1993, p. 47) recognised that, “Apart from the lower Barremian occurrence in the Barents Sea, the species (B. shaftesburiense) seems to be restricted to the Albian”. An Albian FAD for B. shaftesburiense was further confirmed in Nøhr-Hansen et al. (2019, p. 24, 25), where it was described “in the middle part” of Subzone Litosphaeridium arundum (1) of Nøhr-Hansen (1993), middle Albian.
The observed range of Batioladinium mucronatum at Speeton was between Beds LB6 and LB2D (early Barremian, top variabilis to fissicostatum Zones), and the FAD of Tenua anaphrissa was immediately above this range, in Bed LB1, suggesting a very similar range for B. mucronatum to that observed by Århus et al. (op. cit.).