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Heterosphaeridium bellii
Heterosphaeridium bellii Radmacher et al., 2014, p.31–33, pl.1, figs.1–9.
Holotype: Radmacher et al., 2014, pl.1, figs.1–3,9.
Age: late Campanian–Maastrichtian.
Original description: Radmacher et al., 2013:
Heterosphaeridium bellii sp. nov.
Synonyms:
2011 Heterosphaeridium heteracanthum (Deflandre and Cookson, 1955) Eisenack and Kjellström, 1972 — Palamarczuk and Landman: 148, pl. 5, fig. c.
2012 Heterosphaeridium heteracanthum (Deflandre and Cookson, 1955) Eisenack and Kjellström, 1972 — Nøhr-Hansen: 70, pl. 6, fig. 2.
Holotype: well 7120/7-3, sample 1370, England Finder reference H39/4, Plate I, 1-3, 9.
Paratype: well 7120/7-3, depth 1370 m, EF reference M41/1, Plate I, 4, 5.
Repository: PMO 224.498; lodged at the Paleontological Museum of Oslo, Norway.
Type stratum and locality: Southwestern Barents Sea, well 7120/7-3, Torsk Fm., at 1370 m.
Etymology: Named in honour of David Graham Bell, an expert on the Cretaceous palynology of the Norwegian Continental Shelf.
Diagnosis: Gonyaulacacean, chorate cyst with an apical archaeopyle and non-tabular processes which have subequal length, but vary in shape. The processes may be solid or hollow. Their endings are variable, but the majority have a characteristic “scythe-like ” termination with irregularly jagged ridges (Plate I, 9). The processes are never connected distally but may be connected proximally by very low crests. A paratabulation pattern has not been observed.
Description: The specimens possess an apical archaeopyle formed by the loss of presumably four antapical plates and only rarely detached, contiguous opercula were identified. Paratabulation is absent, reflected only by the archaeopyle that occasionally has a visible sulcal notch. Wall layers are adpressed and appear to be autophragm only. Wall ornamentation displayed by the examined specimens varies from being smooth to finely punctate or striate. Numerous non-tabular processes of sub-equal length are characterised by differently-developed endings. The “scythe-like ” terminations with jagged ridges (Plate I, 9) occur on the majority of the processes. The remaining processes are usually opened distally. A single specimen of Heterosphaeridium bellii sp. nov. possesses both solid and hollow processes, which can also be hollow basally and distally, but closed in the middle. The processes that never show a distal connection can be connected by very low crests that do not exceed 2 μm in height. The cyst body is often round to ovoidal, with an average diameter of 47 μm and the processes length 16 μm (twelve specimens measured). The holotype diameter equals 47.4 μm and the average process length is 15.2 μm (seven processes measured). The “scythe-like ” endings are usually not wider than 5.2 μm.
Discussion: The newly described species Heterosphaeridium bellii is well-known in the hydrocarbon industry as Cleistosphaeridium sp. 1, Heterosphaeridium cf. heteracanthum or Heterosphaeridium sp. A. The differences between the genera Cleistosphaeridium and Heterosphaeridium relate to the nature of processes and their linkage. Davey et al. (1966, p. 166) described Cleistosphaeridium as an ovoidal, chorate cyst that is “typically closed distally and without communication to endocoel”. Similarly, Stover and Evitt (1978) stated in their diagnosis that the processes of Cleistosphaeridium have similar size and shape and are closed distally. In contrast, Heterosphaeridium includes forms which possess two or three types of different processes in one specimen (Yun, 1981). The distal and proximal process linkage is a significant feature in Heterosphaeridium. The new species, H. bellii, possesses different types of processes in one specimen and some of them are proximally linked. They also possess different shapes of process endings which often are opened distally. Thus, H. bellii sp. nov. is assigned to Heterosphaeridium
Comparison. Heterosphaeridium conjunctum has processes equal in length but more variable in width and narrowing towards the tips. Heterosphaeridium cordiforme has simpler and fewer processes covering a heart-shaped body. Heterosphaeridium spinaconjunctum and Heterosphaeridium verdieri have processes that are connected distally. Heterosphaeridium bellii sp. nov. differs significantly from Heterosphaeridium difficile by lack of the conspicuously wide processes occurring together with slimmer ones. Differences between H. bellii and Heterosphaeridium heteracanthum are provided below (see emendation).
Stratigraphic range: According to the authors' observation Heterosphaeridium bellii sp. nov. occurs extensively throughout the Barents Sea (e.g. boreholes 7119/12-1, 7120/5-1, 7121/5-1) and the Norwegian Sea (6707/10-1, 6711/4-U-1). In addition, an increase in a comparable species called Heterosphaeridium cf. H. heteracanthum or H. heteracanthum was observed in the Late Campanian Baculites compressus–Baculites cuneatus–Baculites reesidei ammonite zones in the Western Interior Basin (Palamarczuk and Landman, 2011). The specimen of H. heteracanthum provided by Palamarczuk and Landman (2011) strongly resembles H. bellii sp. nov. and the interval characterised by its dominance (57% of the assemblage) is similar to that observed within the H. bellii acme from the Barents Sea. Thus, we assume that they are the same species. In this study, the acme of Heterosphaeridium bellii sp. nov. occurs together with Late Campanian species and above the LAO of Palaeoglenodinium cretaceum, which according to Costa and Davey (1992) is characteristic of the Early Campanian age. The LSAO of H. bellii sp. nov. coincides with the LO of Raetiaedinium truncigerum indicating a Late Campanian age (Williams et al., 2004). The LCO of H. bellii sp. nov. has been recorded together with or just above the LO of Odontochitina operculata and the LCO of Spongodinium delitiense suggesting a Campanian to Maastrichtian age. An abundant occurrence of S. delitiense was previously recorded in the Late Campanian by Nagy et al. (1997). The LO of O. operculata may indicate the Early Maastrichtian according to Costa and Davey (1992), Williams et al. (2004), Schiøler and Wilson (2001), and Antonescu et al. (2001).
Holotype: Radmacher et al., 2014, pl.1, figs.1–3,9.
Age: late Campanian–Maastrichtian.
Original description: Radmacher et al., 2013:
Heterosphaeridium bellii sp. nov.
Synonyms:
2011 Heterosphaeridium heteracanthum (Deflandre and Cookson, 1955) Eisenack and Kjellström, 1972 — Palamarczuk and Landman: 148, pl. 5, fig. c.
2012 Heterosphaeridium heteracanthum (Deflandre and Cookson, 1955) Eisenack and Kjellström, 1972 — Nøhr-Hansen: 70, pl. 6, fig. 2.
Holotype: well 7120/7-3, sample 1370, England Finder reference H39/4, Plate I, 1-3, 9.
Paratype: well 7120/7-3, depth 1370 m, EF reference M41/1, Plate I, 4, 5.
Repository: PMO 224.498; lodged at the Paleontological Museum of Oslo, Norway.
Type stratum and locality: Southwestern Barents Sea, well 7120/7-3, Torsk Fm., at 1370 m.
Etymology: Named in honour of David Graham Bell, an expert on the Cretaceous palynology of the Norwegian Continental Shelf.
Diagnosis: Gonyaulacacean, chorate cyst with an apical archaeopyle and non-tabular processes which have subequal length, but vary in shape. The processes may be solid or hollow. Their endings are variable, but the majority have a characteristic “scythe-like ” termination with irregularly jagged ridges (Plate I, 9). The processes are never connected distally but may be connected proximally by very low crests. A paratabulation pattern has not been observed.
Description: The specimens possess an apical archaeopyle formed by the loss of presumably four antapical plates and only rarely detached, contiguous opercula were identified. Paratabulation is absent, reflected only by the archaeopyle that occasionally has a visible sulcal notch. Wall layers are adpressed and appear to be autophragm only. Wall ornamentation displayed by the examined specimens varies from being smooth to finely punctate or striate. Numerous non-tabular processes of sub-equal length are characterised by differently-developed endings. The “scythe-like ” terminations with jagged ridges (Plate I, 9) occur on the majority of the processes. The remaining processes are usually opened distally. A single specimen of Heterosphaeridium bellii sp. nov. possesses both solid and hollow processes, which can also be hollow basally and distally, but closed in the middle. The processes that never show a distal connection can be connected by very low crests that do not exceed 2 μm in height. The cyst body is often round to ovoidal, with an average diameter of 47 μm and the processes length 16 μm (twelve specimens measured). The holotype diameter equals 47.4 μm and the average process length is 15.2 μm (seven processes measured). The “scythe-like ” endings are usually not wider than 5.2 μm.
Discussion: The newly described species Heterosphaeridium bellii is well-known in the hydrocarbon industry as Cleistosphaeridium sp. 1, Heterosphaeridium cf. heteracanthum or Heterosphaeridium sp. A. The differences between the genera Cleistosphaeridium and Heterosphaeridium relate to the nature of processes and their linkage. Davey et al. (1966, p. 166) described Cleistosphaeridium as an ovoidal, chorate cyst that is “typically closed distally and without communication to endocoel”. Similarly, Stover and Evitt (1978) stated in their diagnosis that the processes of Cleistosphaeridium have similar size and shape and are closed distally. In contrast, Heterosphaeridium includes forms which possess two or three types of different processes in one specimen (Yun, 1981). The distal and proximal process linkage is a significant feature in Heterosphaeridium. The new species, H. bellii, possesses different types of processes in one specimen and some of them are proximally linked. They also possess different shapes of process endings which often are opened distally. Thus, H. bellii sp. nov. is assigned to Heterosphaeridium
Comparison. Heterosphaeridium conjunctum has processes equal in length but more variable in width and narrowing towards the tips. Heterosphaeridium cordiforme has simpler and fewer processes covering a heart-shaped body. Heterosphaeridium spinaconjunctum and Heterosphaeridium verdieri have processes that are connected distally. Heterosphaeridium bellii sp. nov. differs significantly from Heterosphaeridium difficile by lack of the conspicuously wide processes occurring together with slimmer ones. Differences between H. bellii and Heterosphaeridium heteracanthum are provided below (see emendation).
Stratigraphic range: According to the authors' observation Heterosphaeridium bellii sp. nov. occurs extensively throughout the Barents Sea (e.g. boreholes 7119/12-1, 7120/5-1, 7121/5-1) and the Norwegian Sea (6707/10-1, 6711/4-U-1). In addition, an increase in a comparable species called Heterosphaeridium cf. H. heteracanthum or H. heteracanthum was observed in the Late Campanian Baculites compressus–Baculites cuneatus–Baculites reesidei ammonite zones in the Western Interior Basin (Palamarczuk and Landman, 2011). The specimen of H. heteracanthum provided by Palamarczuk and Landman (2011) strongly resembles H. bellii sp. nov. and the interval characterised by its dominance (57% of the assemblage) is similar to that observed within the H. bellii acme from the Barents Sea. Thus, we assume that they are the same species. In this study, the acme of Heterosphaeridium bellii sp. nov. occurs together with Late Campanian species and above the LAO of Palaeoglenodinium cretaceum, which according to Costa and Davey (1992) is characteristic of the Early Campanian age. The LSAO of H. bellii sp. nov. coincides with the LO of Raetiaedinium truncigerum indicating a Late Campanian age (Williams et al., 2004). The LCO of H. bellii sp. nov. has been recorded together with or just above the LO of Odontochitina operculata and the LCO of Spongodinium delitiense suggesting a Campanian to Maastrichtian age. An abundant occurrence of S. delitiense was previously recorded in the Late Campanian by Nagy et al. (1997). The LO of O. operculata may indicate the Early Maastrichtian according to Costa and Davey (1992), Williams et al. (2004), Schiøler and Wilson (2001), and Antonescu et al. (2001).