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Glaphyrocysta granulosa
Glaphyrocysta granulosa sp. nov., Vieira et al., 2020
Holotype: Plate II, 1 and 2, Vieira et al., 2020
Age: Selandian Stage of Paleocene
Locality: Foinaven and Schiehallion Fields
Original description: Vieira et al., 2020:
Diagnosis:
Proximochorate to chorate dinoflagellate cyst of intermediate size. The archeopyle is apical (type tA) and well-defined. The endophragm is moderately thick and covered with coarse irregular ornament in the form of grana, coni, and possibly small verrucae, which may be randomly distributed.
Description:
Proximochorate to chorate cyst of intermediate size. Subspherical in shape with rounded apex and antapex with a single small lobe at the base sometimes observed. The central body is usually flattened in the dorso-ventral area.
Archeopyle: apical (type tA) with a well-defined zig-zag margin, operculum free, and bearing (if present) similar processes to the rest of the dinoflagellate cyst.
Wall: layers could not be determined; the dinoflagellate cyst probably has two layers adpressed between processes. Smooth and thin periphragm and moderately thick endophragm; wall surface is covered with coarse ornament in the form of grana, coni, and possibly small verrucae which may be irregularly distributed.
Processes: restricted to the peripheral zone of the cyst body with most of the mid-ventral and mid-dorsal areas often devoid of processes. These processes are joined proximally in linear or arcuate complexes and usually with only a few connected distally by irregularly broad trabeculae terminations; the outer edge of the trabeculae is serrate to finally denticulate. These processes are occasionally, short, truncated and solid with simple acuminate or bifid tips arising from the central body. The length of the processes rarely exceeds one-third of the diameter of central body.
Tabulation: indistinct and may be indicated only by the margin of the archeopyle but is apparently gonyaulacacean. Sulcus usually only distinct by a shallow sulcular notch
in the apical margin.
Dimensions:
Central body length (without operculum) 48(64)69 μm, width 58(67)70 μm, process length 16(18)21 μm.
25 specimens measured
Affinities/Comparison:
Glaphyrocysta ordinata (Williams and Downie, 1966) Stover and Evitt, 1978 has the closest resemblance to the present species although Glaphyrocysta granulosa sp. nov. differs by exhibiting more robust processes with only a few connected distally by irregularly broad trabeculae terminations. The cyst wall is also slightly thicker and
exhibits a relatively dense granulate central body. Glaphyrocysta semitecta (Bujak, 1980) Lentin and Williams (1981) differs by lacking a fenestrate process stem and having a high perforate membrane.
When compared with the Late Maastrichtian-Danian type Glaphyrocysta perforata described by Hultberg and Malmgren (1985), it can be suggested that the processes of G. granulosa sp. nov. do not fuse within a perforate periphragm, whereas in G. perforata distally changes into a homogeneous, almost non-perforate periphragm with
no indication of the processes terminating with an irregular margin.
Holotype: Plate II, 1 and 2, Vieira et al., 2020
Age: Selandian Stage of Paleocene
Locality: Foinaven and Schiehallion Fields
Original description: Vieira et al., 2020:
Diagnosis:
Proximochorate to chorate dinoflagellate cyst of intermediate size. The archeopyle is apical (type tA) and well-defined. The endophragm is moderately thick and covered with coarse irregular ornament in the form of grana, coni, and possibly small verrucae, which may be randomly distributed.
Description:
Proximochorate to chorate cyst of intermediate size. Subspherical in shape with rounded apex and antapex with a single small lobe at the base sometimes observed. The central body is usually flattened in the dorso-ventral area.
Archeopyle: apical (type tA) with a well-defined zig-zag margin, operculum free, and bearing (if present) similar processes to the rest of the dinoflagellate cyst.
Wall: layers could not be determined; the dinoflagellate cyst probably has two layers adpressed between processes. Smooth and thin periphragm and moderately thick endophragm; wall surface is covered with coarse ornament in the form of grana, coni, and possibly small verrucae which may be irregularly distributed.
Processes: restricted to the peripheral zone of the cyst body with most of the mid-ventral and mid-dorsal areas often devoid of processes. These processes are joined proximally in linear or arcuate complexes and usually with only a few connected distally by irregularly broad trabeculae terminations; the outer edge of the trabeculae is serrate to finally denticulate. These processes are occasionally, short, truncated and solid with simple acuminate or bifid tips arising from the central body. The length of the processes rarely exceeds one-third of the diameter of central body.
Tabulation: indistinct and may be indicated only by the margin of the archeopyle but is apparently gonyaulacacean. Sulcus usually only distinct by a shallow sulcular notch
in the apical margin.
Dimensions:
Central body length (without operculum) 48(64)69 μm, width 58(67)70 μm, process length 16(18)21 μm.
25 specimens measured
Affinities/Comparison:
Glaphyrocysta ordinata (Williams and Downie, 1966) Stover and Evitt, 1978 has the closest resemblance to the present species although Glaphyrocysta granulosa sp. nov. differs by exhibiting more robust processes with only a few connected distally by irregularly broad trabeculae terminations. The cyst wall is also slightly thicker and
exhibits a relatively dense granulate central body. Glaphyrocysta semitecta (Bujak, 1980) Lentin and Williams (1981) differs by lacking a fenestrate process stem and having a high perforate membrane.
When compared with the Late Maastrichtian-Danian type Glaphyrocysta perforata described by Hultberg and Malmgren (1985), it can be suggested that the processes of G. granulosa sp. nov. do not fuse within a perforate periphragm, whereas in G. perforata distally changes into a homogeneous, almost non-perforate periphragm with
no indication of the processes terminating with an irregular margin.