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Glaphyrocysta shetlandensis
Glaphyrocysta shetlandensis sp. nov., Vieira et al., 2020
Holotype: Plate II, 1, 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. Archeopyle is apical and well-defined. The endophragm is moderately thick and the central body usually bald to punctate.
Description:
Proximochorate to chorate cyst of intermediate size, sub-spherical 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 dorsoventral area.
Archeopyle: apical (type tA) and well-defined, exhibiting a typical zig-zag margin;
Operculum: usually free but occasionally present.
Wall: The dinoflagellate cyst consists of two layers (periphragm and endophragm) adpressed between processes with a moderately thick, bald to punctate central body. Processes: Most of the mid-ventral and mid-dorsal areas are often devoid of processes (Plate II). However, occasionally short, truncated and solid processes with simple acuminate or bifid tips occur on the central body. Process length rarely exceeds one-third of the diameter of central body. These processes appear restricted to the peripheral zone of the cyst body and are joined proximally in linear or arcuate complexes. Only a few processes are connected distally by an irregularly broad trabeculae termination; the outer edge of the trabeculae is serrate to finally denticulate.
Cyst tabulation: indistinct, and may be indicated only by the margin of the archaeopyle but is apparently of a gonyaulacacean type. The sulcus is usually only observed by a shallow sulcul notch in the apical margin.
Dimensions:
Central body length 52(67)76 μm, width 59(68)73 μm, process length 10(16)25 μm. Number of specimens measured = 25.
Affinities:
Glaphyrocysta shetlandensis sp. nov., is most similar to Glaphyrocysta ordinata (Williams and Downie, 1966) Stover and Evitt, 1978, however this new specie differs from the holotype of G. ordinata (Williams and Downie, 1966, pl. 25, 3) by exhibiting short, truncated and solid processes with only a few connected distally by irregularly broad trabeculae terminations. In addition, the cyst wall is thicker with a bald to finely punctate central body.
Glaphyrocysta shetlandensis sp. nov. also closely resembles the other new species described here as G. granulosa sp. nov., although it lacks the dense granulate surface ornament which helps to clearly distinguish between both species. Both new species have a sub-spherical/sub-circular outline. However, more often G. granulosa sp. nov. is broader than G. shetlandensis sp. nov. Additionally, the latter species occasionally shows that the archeopyle is attached. The two new species may also exhibit a gradational relationship between themselves regarding the degree of ornamentation of the cyst wall as shown on Plate II, 3.
Holotype: Plate II, 1, 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. Archeopyle is apical and well-defined. The endophragm is moderately thick and the central body usually bald to punctate.
Description:
Proximochorate to chorate cyst of intermediate size, sub-spherical 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 dorsoventral area.
Archeopyle: apical (type tA) and well-defined, exhibiting a typical zig-zag margin;
Operculum: usually free but occasionally present.
Wall: The dinoflagellate cyst consists of two layers (periphragm and endophragm) adpressed between processes with a moderately thick, bald to punctate central body. Processes: Most of the mid-ventral and mid-dorsal areas are often devoid of processes (Plate II). However, occasionally short, truncated and solid processes with simple acuminate or bifid tips occur on the central body. Process length rarely exceeds one-third of the diameter of central body. These processes appear restricted to the peripheral zone of the cyst body and are joined proximally in linear or arcuate complexes. Only a few processes are connected distally by an irregularly broad trabeculae termination; the outer edge of the trabeculae is serrate to finally denticulate.
Cyst tabulation: indistinct, and may be indicated only by the margin of the archaeopyle but is apparently of a gonyaulacacean type. The sulcus is usually only observed by a shallow sulcul notch in the apical margin.
Dimensions:
Central body length 52(67)76 μm, width 59(68)73 μm, process length 10(16)25 μm. Number of specimens measured = 25.
Affinities:
Glaphyrocysta shetlandensis sp. nov., is most similar to Glaphyrocysta ordinata (Williams and Downie, 1966) Stover and Evitt, 1978, however this new specie differs from the holotype of G. ordinata (Williams and Downie, 1966, pl. 25, 3) by exhibiting short, truncated and solid processes with only a few connected distally by irregularly broad trabeculae terminations. In addition, the cyst wall is thicker with a bald to finely punctate central body.
Glaphyrocysta shetlandensis sp. nov. also closely resembles the other new species described here as G. granulosa sp. nov., although it lacks the dense granulate surface ornament which helps to clearly distinguish between both species. Both new species have a sub-spherical/sub-circular outline. However, more often G. granulosa sp. nov. is broader than G. shetlandensis sp. nov. Additionally, the latter species occasionally shows that the archeopyle is attached. The two new species may also exhibit a gradational relationship between themselves regarding the degree of ornamentation of the cyst wall as shown on Plate II, 3.