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Spiniferites ramosus subsp. ginakrogiae
Spiniferites ramosus subsp. ginakrogiae subsp. nov., Pearce, M. A., 2018, p. 76-78
Holotype: Pearce, M. A., 2018, Pl. 2, figs. 1–3.
Type locality and horizon: Upper Chalk (Burnham Chalk Formation)
Stratigraphic range: Lower Cenomanian: Lower Campanian
Original description: Pearce, M. A., 2018:
Diagnosis:
A large subspecies of Spiniferites ramosus with a smooth wall, narrow sutural crests and intergonal processes on some of the larger plate boundaries.
Description:
Large, spiniferate, chorate dinoflagellate cyst with a sub-spherical central body.
Wall: two-layered with a thick (∼ 2 μm) and smooth endophragm and a thin (∼ 0.5 μm) periphragm, the latter of which develops solid processes.
Processes: Distally trifurcating gonal and bifurcating intergonal processes (on the boundaries between the larger precingular, cingular and postcingular plates) are typically less than one-third the central body diameter, with the furcation occurring from 50 % (on shorter processes) to 25 % (on longer processes) from the distal end. Narrow sutural crests line the processes, often to the distal extremity, occasionally rendering the bi- and trifurcations relatively wide, and define a clear standard gonyaulacacean tabulation.
The cingulum is weakly laevorotatory, typically by one cingulum width; the parasulcus lacks clearly developed sutures.
Archaeopyle: precingular, Type P3′′ , operculum detached.
Dimensions:
Holotype: central body w/ l: 74 × 75 μm, maximum process length = 22 μm
paratype 1: central body w/ l: 71 × 76 μm, maximum process length = 29 μm,
paratype 2: central body w/ l: 91 × 80 μm, maximum process length = 19 μm.
Range central body w/ l = 54(69)91 μm × 50(69)84 μm, maximum process length, 15(21)30 μm
Twenty specimens measured.
Remarks:
This species appears to be morphologically intermediate between Spiniferites ramosus subsp. gracilis (by possessing intergonal processes) and Spiniferites porosus (in size). The central body diameter of Spiniferites porosus ranges from 66 to 69 μm (the holotype is 66 × 75 μm), with process lengths ranging from 17 to 36 μm (holotype 17–23 μm) long.
Affinities/Comparison:
Differs from other subspecies of Spiniferites ramosus by its conspicuously large size.
Holotype: Pearce, M. A., 2018, Pl. 2, figs. 1–3.
Type locality and horizon: Upper Chalk (Burnham Chalk Formation)
Stratigraphic range: Lower Cenomanian: Lower Campanian
Original description: Pearce, M. A., 2018:
Diagnosis:
A large subspecies of Spiniferites ramosus with a smooth wall, narrow sutural crests and intergonal processes on some of the larger plate boundaries.
Description:
Large, spiniferate, chorate dinoflagellate cyst with a sub-spherical central body.
Wall: two-layered with a thick (∼ 2 μm) and smooth endophragm and a thin (∼ 0.5 μm) periphragm, the latter of which develops solid processes.
Processes: Distally trifurcating gonal and bifurcating intergonal processes (on the boundaries between the larger precingular, cingular and postcingular plates) are typically less than one-third the central body diameter, with the furcation occurring from 50 % (on shorter processes) to 25 % (on longer processes) from the distal end. Narrow sutural crests line the processes, often to the distal extremity, occasionally rendering the bi- and trifurcations relatively wide, and define a clear standard gonyaulacacean tabulation.
The cingulum is weakly laevorotatory, typically by one cingulum width; the parasulcus lacks clearly developed sutures.
Archaeopyle: precingular, Type P3′′ , operculum detached.
Dimensions:
Holotype: central body w/ l: 74 × 75 μm, maximum process length = 22 μm
paratype 1: central body w/ l: 71 × 76 μm, maximum process length = 29 μm,
paratype 2: central body w/ l: 91 × 80 μm, maximum process length = 19 μm.
Range central body w/ l = 54(69)91 μm × 50(69)84 μm, maximum process length, 15(21)30 μm
Twenty specimens measured.
Remarks:
This species appears to be morphologically intermediate between Spiniferites ramosus subsp. gracilis (by possessing intergonal processes) and Spiniferites porosus (in size). The central body diameter of Spiniferites porosus ranges from 66 to 69 μm (the holotype is 66 × 75 μm), with process lengths ranging from 17 to 36 μm (holotype 17–23 μm) long.
Affinities/Comparison:
Differs from other subspecies of Spiniferites ramosus by its conspicuously large size.