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Thalassiphora lacunata
From Fensome et al., 2019:
Thalassiphora lacunata Vieira et al., 2018, p.260, pl.1, figs.1–7.
Holotype: Vieira et al,, 2018, pl.1, fig.1.
Age: late Danian - early Selandian.
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Original description: Vieira, M. et al. 2018: Thalassiphora lacunata sp. nov.:
Diagnosis:
Cyst two-layered. Endophragm distinct, circular to subcircular, with a thin delicate wall. Periphragm dorsoventrally flattened, with subcircular or ellipsoidal outline and smooth surface.
Description:
The cyst is camocavate. Endophragm and periphragm are widely separated by a large pericoel that completely surrounds the central body, except at the mid-dorsal area, where both layers are in contact. On the dorsal surface, the periphragm is only present on the area where the two layers are closely adpressed and on the adjacent zones of the plate boundaries, which are defined by slight thickenings. The remaining periphragm surface is absent, resulting in the occurrence of large, circular to subcircular
openings with regular margins and different sizes roughly reflecting the tabulation of the dorsal surface. In well-preserved specimens, seven to eight openings are visible, four on the anterior part of the cyst and four on the posterior part. The archeopyle is precingular, formed by the displacement of the 3′′ plate, only apparent in well-preserved specimens. Operculum is free.
Dimensions:
Diameter of pericyst 70 (83.5) 94.5 μm, Endocyst 31 (40) 47 μm, Pericoel 21 (28) 35 μm.
Number of specimens measured:18.
Affinities:
This species is morphologically very similar to Thalassiphora delicata Williams and Downie (1966) (Pl. I, 8), from which it differs by possessing large, subcircular openings on the dorsal surface of the periphragm. Both species co-occur in the ‘latest’ Danian and ‘early’ Selandian of the North Sea, but the stratigraphic range of T. delicata is significantly broader, ranging from Danian to Bartonian.
Thalassiphora pelagica (Eisenack 1954) Benedek and Gocht (1981) and T. delicata possess a large ventral opening in the periphragm. In the latter species, it is formed by the loss of paraplate 1′′ according to Eaton (1976) and Manum (1979). These hollows have not been observed in T. lacunata sp. nov. Thalassiphora inflata Heilmann-Clausen in Thomsen and Heilmann-Clausen (1985) (Pl. I, 9) differs in its smaller size and the absence of pericoel in the antapical area. The dinoflagellate cyst species Thalassiphora rota, described by Schiøler (2005), bears a resemblance with T. lacunata, but it differs from the new species in having processes that connect the inner body with the periphragm. Thalassiphora fenestrata Liengjarern et al. (1980) also develops fenestration of the periphragm, but perforations are clearly smaller, irregular and more numerous.
Thalassiphora lacunata Vieira et al., 2018, p.260, pl.1, figs.1–7.
Holotype: Vieira et al,, 2018, pl.1, fig.1.
Age: late Danian - early Selandian.
---------------------------------------------------------------------------------------------------
Original description: Vieira, M. et al. 2018: Thalassiphora lacunata sp. nov.:
Diagnosis:
Cyst two-layered. Endophragm distinct, circular to subcircular, with a thin delicate wall. Periphragm dorsoventrally flattened, with subcircular or ellipsoidal outline and smooth surface.
Description:
The cyst is camocavate. Endophragm and periphragm are widely separated by a large pericoel that completely surrounds the central body, except at the mid-dorsal area, where both layers are in contact. On the dorsal surface, the periphragm is only present on the area where the two layers are closely adpressed and on the adjacent zones of the plate boundaries, which are defined by slight thickenings. The remaining periphragm surface is absent, resulting in the occurrence of large, circular to subcircular
openings with regular margins and different sizes roughly reflecting the tabulation of the dorsal surface. In well-preserved specimens, seven to eight openings are visible, four on the anterior part of the cyst and four on the posterior part. The archeopyle is precingular, formed by the displacement of the 3′′ plate, only apparent in well-preserved specimens. Operculum is free.
Dimensions:
Diameter of pericyst 70 (83.5) 94.5 μm, Endocyst 31 (40) 47 μm, Pericoel 21 (28) 35 μm.
Number of specimens measured:18.
Affinities:
This species is morphologically very similar to Thalassiphora delicata Williams and Downie (1966) (Pl. I, 8), from which it differs by possessing large, subcircular openings on the dorsal surface of the periphragm. Both species co-occur in the ‘latest’ Danian and ‘early’ Selandian of the North Sea, but the stratigraphic range of T. delicata is significantly broader, ranging from Danian to Bartonian.
Thalassiphora pelagica (Eisenack 1954) Benedek and Gocht (1981) and T. delicata possess a large ventral opening in the periphragm. In the latter species, it is formed by the loss of paraplate 1′′ according to Eaton (1976) and Manum (1979). These hollows have not been observed in T. lacunata sp. nov. Thalassiphora inflata Heilmann-Clausen in Thomsen and Heilmann-Clausen (1985) (Pl. I, 9) differs in its smaller size and the absence of pericoel in the antapical area. The dinoflagellate cyst species Thalassiphora rota, described by Schiøler (2005), bears a resemblance with T. lacunata, but it differs from the new species in having processes that connect the inner body with the periphragm. Thalassiphora fenestrata Liengjarern et al. (1980) also develops fenestration of the periphragm, but perforations are clearly smaller, irregular and more numerous.