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Echinidinium sleipnerense
Echinidinium sleipnerense Head and Riding in Head et al., 2004, p.294, figs.4Q–S,5A–C.
Holotype: Head et al., 2004, figs.5A–C.
Age: Gelasian.
Original description (Head et al., 2004):
Echinidinium sleipnerensis Head and Riding sp. nov. Figs. 4Q–S and 5A–C
Diagnosis. A species of Echinidinium whose smooth central body surface bears long, densely distributed, acuminate processes. Processes generally have hollow, expanded bases, and are solid for most of their length; occasional processes are solid throughout. Processes are circular in transverse section. Archeopyle theropylic consisting of a straight split extending at least half-way around the cyst. No other expression of tabulation.
Description. Central body surface smooth, but may bear sparsely scattered spinules and granules less than 0.3 µm in diameter. The central body wall is thin (less than 0.3 µm) and shows no stratification under light microscopy except at process bases. Both central body and processes are light to medium brown. Processes are numerous and distributed over entire surface, adjacent processes being separated by about 1.5–3.0 µm at their base. Processes are solid for most of length but bases, generally 1.0–1.5 mm in diameter, are usually hollow and expanded. Occasional thin processes have solid bases that are only weakly expanded. All processes have a smooth surface and taper to a fine point. The archeopyle (indicated by an arrow in Figs. 4Q and 5B), possibly following a cingular margin, consists of a straight or nearly straight split extending at least half-way around the cyst.
Measurements.
Holotype: central body diameter 46 x 43 µm, maximum process length 8 µm.
Range: maximum central body diameter 41 (44.3) 48 µm, maximum process length 5 (6.2) 8 µm. Six specimens were measured.
Etymology. Named after the Sleipner Field area, northern North Sea, which serves as the type locality for this species.
Holotype. Fig. 5A–C. BGS specimen MPK 12803, slide 1, England Finder reference G30/0. Sample MPA 51092, at 906.00 m depth in Norwegian sector well 15/9-A-11. Curated at the British Geological Survey, Nottingham, UK.
Comparison. The apiculocavate and acuminate nature of the processes on Echinidinium sleipnerensis together distinguish this species from all others of the genus. Echinidinium zonneveldiae Head, 2003b and ‘Echinidinium transparantum’ Zonneveld (1997) both differ in having processes that are solid and colourless to pale brown, and in having some processes with rectangular basal crosssections. Echinidinium? sp. 1 of this study is similar to Echinidinium sleipnerensis but is smaller (a central body diameter of 25–32 mm), and has an uncertain style of archeopyle. Islandinium minutum (Harland and Reid in Harland, Reid, Dobell & Norris, 1980) Head et al., 2001, although superficially similar to Echinidinium sleipnerensis in size and process morphology, has a granulate central body surface and apical archeopyle.
Holotype: Head et al., 2004, figs.5A–C.
Age: Gelasian.
Original description (Head et al., 2004):
Echinidinium sleipnerensis Head and Riding sp. nov. Figs. 4Q–S and 5A–C
Diagnosis. A species of Echinidinium whose smooth central body surface bears long, densely distributed, acuminate processes. Processes generally have hollow, expanded bases, and are solid for most of their length; occasional processes are solid throughout. Processes are circular in transverse section. Archeopyle theropylic consisting of a straight split extending at least half-way around the cyst. No other expression of tabulation.
Description. Central body surface smooth, but may bear sparsely scattered spinules and granules less than 0.3 µm in diameter. The central body wall is thin (less than 0.3 µm) and shows no stratification under light microscopy except at process bases. Both central body and processes are light to medium brown. Processes are numerous and distributed over entire surface, adjacent processes being separated by about 1.5–3.0 µm at their base. Processes are solid for most of length but bases, generally 1.0–1.5 mm in diameter, are usually hollow and expanded. Occasional thin processes have solid bases that are only weakly expanded. All processes have a smooth surface and taper to a fine point. The archeopyle (indicated by an arrow in Figs. 4Q and 5B), possibly following a cingular margin, consists of a straight or nearly straight split extending at least half-way around the cyst.
Measurements.
Holotype: central body diameter 46 x 43 µm, maximum process length 8 µm.
Range: maximum central body diameter 41 (44.3) 48 µm, maximum process length 5 (6.2) 8 µm. Six specimens were measured.
Etymology. Named after the Sleipner Field area, northern North Sea, which serves as the type locality for this species.
Holotype. Fig. 5A–C. BGS specimen MPK 12803, slide 1, England Finder reference G30/0. Sample MPA 51092, at 906.00 m depth in Norwegian sector well 15/9-A-11. Curated at the British Geological Survey, Nottingham, UK.
Comparison. The apiculocavate and acuminate nature of the processes on Echinidinium sleipnerensis together distinguish this species from all others of the genus. Echinidinium zonneveldiae Head, 2003b and ‘Echinidinium transparantum’ Zonneveld (1997) both differ in having processes that are solid and colourless to pale brown, and in having some processes with rectangular basal crosssections. Echinidinium? sp. 1 of this study is similar to Echinidinium sleipnerensis but is smaller (a central body diameter of 25–32 mm), and has an uncertain style of archeopyle. Islandinium minutum (Harland and Reid in Harland, Reid, Dobell & Norris, 1980) Head et al., 2001, although superficially similar to Echinidinium sleipnerensis in size and process morphology, has a granulate central body surface and apical archeopyle.