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Senoniasphaera porosa
Senoniasphaera porosa sp. nov., Vieira and Mahdi, 2021
Holotype: Plate 6, figure 1, Vieira and Mahdi, 2021
Type locality: Møre Basin (Norway)
Stratigraphic extent: Late Cretaceous, middle-late Campanian
Original description: Vieira and Mahdi, 2021:
Diagnosis:
Proximate, semi-circular to pentagonal dinoflagellate cyst, with two layers. The periphragm is usually thin and hyaline, with an ornament ranging from fine to coarse pores
and minutely reticulate, the endophragm is relatively thicker (up to 2 µm). The cyst bears two poorly developed lateral protrusions and two antapical horns.
Description:
Proximate, circumcavate, of intermediate size, semi-circular to pentagonal dinoflagellate cysts. Central body dorso-ventrally compressed.
Wall: Cyst consists of two layers, the endophragm is relatively thicker (up to 2 µm) and the periphragm is usually thin and hyaline, with an ornament ranging from fine to coarse pores to minutely reticulate. The periphragm also exhibits two antapical horns of unequal size, with the left usually being larger, and two poorly developed lateral horns; these horns are usually shorter than the apical and antapical horns. The antapical margin is rounded and smooth to finely granulate.
Archaeopyle: apical, Type tA, with a well-developed angular suture line indicating six precingular plates.
Operculum: more often seen detached.
Cingulum: usually clear in the equatorial region of the cyst.
Dimensions:
Apical horn present, outer body (length x width) 83 µm x 71 µm, inner body (length x width) 60 µm x 63 µm (5 specimens measured), without apical horn present, inner body (length x width) 58 µm x 76 µm.
20 specimens measured
Affinities/Comparison:
The distinct fine to coarsely perforated to minutely reticulate periphragm differentiates this new species, from other species within the genus.
Senoniasphaera rotundata is the closest in appearance to the present species, although it exhibits more robust processes, and the cyst wall is moderately thicker with a relatively dense granulate central body. Renidinium gracile differs from the new species by having finer perforations. Prince et al. (1999, p. 161) considered R. gracile to be a junior synonym of S. rotundata. We agree with this observation.
Holotype: Plate 6, figure 1, Vieira and Mahdi, 2021
Type locality: Møre Basin (Norway)
Stratigraphic extent: Late Cretaceous, middle-late Campanian
Original description: Vieira and Mahdi, 2021:
Diagnosis:
Proximate, semi-circular to pentagonal dinoflagellate cyst, with two layers. The periphragm is usually thin and hyaline, with an ornament ranging from fine to coarse pores
and minutely reticulate, the endophragm is relatively thicker (up to 2 µm). The cyst bears two poorly developed lateral protrusions and two antapical horns.
Description:
Proximate, circumcavate, of intermediate size, semi-circular to pentagonal dinoflagellate cysts. Central body dorso-ventrally compressed.
Wall: Cyst consists of two layers, the endophragm is relatively thicker (up to 2 µm) and the periphragm is usually thin and hyaline, with an ornament ranging from fine to coarse pores to minutely reticulate. The periphragm also exhibits two antapical horns of unequal size, with the left usually being larger, and two poorly developed lateral horns; these horns are usually shorter than the apical and antapical horns. The antapical margin is rounded and smooth to finely granulate.
Archaeopyle: apical, Type tA, with a well-developed angular suture line indicating six precingular plates.
Operculum: more often seen detached.
Cingulum: usually clear in the equatorial region of the cyst.
Dimensions:
Apical horn present, outer body (length x width) 83 µm x 71 µm, inner body (length x width) 60 µm x 63 µm (5 specimens measured), without apical horn present, inner body (length x width) 58 µm x 76 µm.
20 specimens measured
Affinities/Comparison:
The distinct fine to coarsely perforated to minutely reticulate periphragm differentiates this new species, from other species within the genus.
Senoniasphaera rotundata is the closest in appearance to the present species, although it exhibits more robust processes, and the cyst wall is moderately thicker with a relatively dense granulate central body. Renidinium gracile differs from the new species by having finer perforations. Prince et al. (1999, p. 161) considered R. gracile to be a junior synonym of S. rotundata. We agree with this observation.