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Thalassiphora microperforata
Thalassiphora microperforata Heilmann-Clausen and Van Simaeys, 2005, p.184,186, pl.13, figs.1–3; pl.14, fig.2.
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.13, figs.1–2.
Age: middle-late Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005):
Thalassiphora microperforata sp. nov. Plate 13, figs. 1–3; Plate 14, fig. 2
Thalassiphora sp. 1, Firth, 1996, pl. 10, fig. 4.
Description. Dinoflagellate cysts of the genus Thalassiphora; cavate, with a dorsoventrally flattened pericyst. The endocyst is subspherical or ellipsoidal, formed by a thin, smooth endophragm. The periphragm is attached to the endocyst midventrally and at the posterior margin of the precingular archeopyle. Elsewhere the phragma are separate. The periphragm encloses the central body except for a relatively small circular opening immediately above the endoarcheopyle. The periphragm is smooth and perforated. The perforations are unevenly distributed. On the ventral surface, the perforations are relatively large and few. The number of perforations increases, and their size decreases, towards the lateral and dorsal surfaces of the periphragm. The paratabulation is only indicated by the archeopyle, which is interpreted as being precingular, Type P (3'' only ).
Derivation of name. From the small holes in the periphragm.
Designation of the holotype. Plate 13, figs. 1, 2, Slide 2644 K3, England Finder coordinates R27. MGUH 27797. Kysing-4 borehole, sample 2644, Middle Eocene. Specimen dimensions: Pericyst diameter 168 µm; endocyst diameter 82 µm.
Designation of the paratype. Paratype 1: Plate 14, fig. 2, Slide 2644 K3, England Finder coordinates G25/4. MGUH 27798. Kysing-4 borehole, sample 2644, Middle Eocene. Paratype 2: Plate 13, fig. 3, Slide 1906 G1, England Finder coordinates S37/2. MGUH 27799. Kysing-3 borehole, sample 1906, Upper Eocene.
Dimensions of measured specimens. Pericyst diameter 141 (146) 174 µm. Endocyst diameter 68 (78) 99 µm. (6 specimens measured).
Comparison. Thalassiphora microperforata sp. nov differs from Thalassiphora pelagica (Eisenack 1954) Eisenack & Gocht 1960 as emended by von Benedek and Gocht, (1981), and from Thalassiphora fenestrata Liengjarern et al. 1980. In both these species the periphragm is only attached to the dorsal side of the central body and forms a large opening on the ventral surface. Thalassiphora microperforata sp. nov. is closely related to Thalassiphora reticulata Morgenroth 1966, which also has a ventrally attached periphragm with a small opening above the archeopyle. Thalassiphora microperforata sp. nov. differs from Thalassiphora reticulata by the membranous periphragm with uneven distribution of small perforations. Only within the range of typical Thalassiphora reticulata were some intermediate specimens between Thalassiphora microperforata and Thalassiphora reticulata encountered. In this study, these intermediate specimens were recorded as Thalassiphora cf. microperforata.
Holotype: Heilmann-Clausen and Van Simaeys, 2005, pl.13, figs.1–2.
Age: middle-late Eocene.
Original description (Heilmann-Clausen and Van Simaeys, 2005):
Thalassiphora microperforata sp. nov. Plate 13, figs. 1–3; Plate 14, fig. 2
Thalassiphora sp. 1, Firth, 1996, pl. 10, fig. 4.
Description. Dinoflagellate cysts of the genus Thalassiphora; cavate, with a dorsoventrally flattened pericyst. The endocyst is subspherical or ellipsoidal, formed by a thin, smooth endophragm. The periphragm is attached to the endocyst midventrally and at the posterior margin of the precingular archeopyle. Elsewhere the phragma are separate. The periphragm encloses the central body except for a relatively small circular opening immediately above the endoarcheopyle. The periphragm is smooth and perforated. The perforations are unevenly distributed. On the ventral surface, the perforations are relatively large and few. The number of perforations increases, and their size decreases, towards the lateral and dorsal surfaces of the periphragm. The paratabulation is only indicated by the archeopyle, which is interpreted as being precingular, Type P (3'' only ).
Derivation of name. From the small holes in the periphragm.
Designation of the holotype. Plate 13, figs. 1, 2, Slide 2644 K3, England Finder coordinates R27. MGUH 27797. Kysing-4 borehole, sample 2644, Middle Eocene. Specimen dimensions: Pericyst diameter 168 µm; endocyst diameter 82 µm.
Designation of the paratype. Paratype 1: Plate 14, fig. 2, Slide 2644 K3, England Finder coordinates G25/4. MGUH 27798. Kysing-4 borehole, sample 2644, Middle Eocene. Paratype 2: Plate 13, fig. 3, Slide 1906 G1, England Finder coordinates S37/2. MGUH 27799. Kysing-3 borehole, sample 1906, Upper Eocene.
Dimensions of measured specimens. Pericyst diameter 141 (146) 174 µm. Endocyst diameter 68 (78) 99 µm. (6 specimens measured).
Comparison. Thalassiphora microperforata sp. nov differs from Thalassiphora pelagica (Eisenack 1954) Eisenack & Gocht 1960 as emended by von Benedek and Gocht, (1981), and from Thalassiphora fenestrata Liengjarern et al. 1980. In both these species the periphragm is only attached to the dorsal side of the central body and forms a large opening on the ventral surface. Thalassiphora microperforata sp. nov. is closely related to Thalassiphora reticulata Morgenroth 1966, which also has a ventrally attached periphragm with a small opening above the archeopyle. Thalassiphora microperforata sp. nov. differs from Thalassiphora reticulata by the membranous periphragm with uneven distribution of small perforations. Only within the range of typical Thalassiphora reticulata were some intermediate specimens between Thalassiphora microperforata and Thalassiphora reticulata encountered. In this study, these intermediate specimens were recorded as Thalassiphora cf. microperforata.