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Deflandrea variabilis
Deflandrea variabilis, Vieira, M. et al., 2018, p. 187
Holotype: Vieira, M. et al., 2018, Plate 3, figure 1
Type locality: southern part of the Ormen Lange field (Norway) over the Danian-aged reservoir
Local stratigraphical range: Danian (Early Paleocene)
Original description: Vieira, M. et al., 2018:
Diagnosis:
Peridinoid, circumcavate to bicavate cyst, sub-circular, ovoidal to elliptical in dorsoventral view.
The cyst is composed of periphragm and endophragm very closely adpressed together; maximum wall separation is in the apical and antapical areas. The periphragm is relatively thin, always smooth to finely granulate and often bearing verrucae up to 2.5 µm in high and width, with a very distinct, short, symmetrically placed apical horn, and with or without two similarly short, well separated antapical horns (of which one is usually reduced). Antapical horns are low and conical with broad bases. Endophragm is spherical to oval in shape, thicker than periphragm and variable in thickness. The epicyst and hypocyst are more or less equal in length; both show rounded to convex lateral sides in outline. Narrow pericoels are well developed and become wider at the apex and antapex. The antapical side and occasionally the antapical horns are well separated, visible with
some low parasutural crests seeming to delimit individual cingular paraplates, but not clear enough to determine the number.
Archaeopyle: Intercalary, occasionally wide, resulting from the detachment of paraplate 2a; paratabulation discernible and usually recognisable.
Dimensions:
Holotype: pericyst length 62.5 µm, breadth 56 µm, endocyst length 47 µm, breadth 53 µm, apical horn 11 µm in length.
25 specimens measured: Pericyst length 38 (62) 78 µm, breadth 27 (52) 63 µm, endocyst length 27 (47) 68 µm, breadth 27 (47) 59 µm,
apical horn 5 (9) 15 µm in length.
Remarks:
This species exhibits considerable intraspecific variation, namely in the ambital outline of the pericyst, the wall structure of both endo- and periphragm, and the shape of the apical and antapical horns. Within the populations examined there is a complete intergradation between forms having greatly reduced antapical horns or simply a rounded antapical margin. The periphragm varies from smooth to occasionally
showing densely scabrate to verrucate sculpture. However, when compared with other Deflandrea types, this form is clearly differentiated.
Nøhr-Hansen et al. (2002) cited several forms as Dinocyst sp. 1 in their fig. 7h–k, Dinocyst sp. 2 in fig. 8a–c, Dinocyst sp. 3e–j and Dinocyst sp. 4k–o, but they did not describe them formally, although these forms have differences when compared with Deflandrea variabilis sp. nov.
Holotype: Vieira, M. et al., 2018, Plate 3, figure 1
Type locality: southern part of the Ormen Lange field (Norway) over the Danian-aged reservoir
Local stratigraphical range: Danian (Early Paleocene)
Original description: Vieira, M. et al., 2018:
Diagnosis:
Peridinoid, circumcavate to bicavate cyst, sub-circular, ovoidal to elliptical in dorsoventral view.
The cyst is composed of periphragm and endophragm very closely adpressed together; maximum wall separation is in the apical and antapical areas. The periphragm is relatively thin, always smooth to finely granulate and often bearing verrucae up to 2.5 µm in high and width, with a very distinct, short, symmetrically placed apical horn, and with or without two similarly short, well separated antapical horns (of which one is usually reduced). Antapical horns are low and conical with broad bases. Endophragm is spherical to oval in shape, thicker than periphragm and variable in thickness. The epicyst and hypocyst are more or less equal in length; both show rounded to convex lateral sides in outline. Narrow pericoels are well developed and become wider at the apex and antapex. The antapical side and occasionally the antapical horns are well separated, visible with
some low parasutural crests seeming to delimit individual cingular paraplates, but not clear enough to determine the number.
Archaeopyle: Intercalary, occasionally wide, resulting from the detachment of paraplate 2a; paratabulation discernible and usually recognisable.
Dimensions:
Holotype: pericyst length 62.5 µm, breadth 56 µm, endocyst length 47 µm, breadth 53 µm, apical horn 11 µm in length.
25 specimens measured: Pericyst length 38 (62) 78 µm, breadth 27 (52) 63 µm, endocyst length 27 (47) 68 µm, breadth 27 (47) 59 µm,
apical horn 5 (9) 15 µm in length.
Remarks:
This species exhibits considerable intraspecific variation, namely in the ambital outline of the pericyst, the wall structure of both endo- and periphragm, and the shape of the apical and antapical horns. Within the populations examined there is a complete intergradation between forms having greatly reduced antapical horns or simply a rounded antapical margin. The periphragm varies from smooth to occasionally
showing densely scabrate to verrucate sculpture. However, when compared with other Deflandrea types, this form is clearly differentiated.
Nøhr-Hansen et al. (2002) cited several forms as Dinocyst sp. 1 in their fig. 7h–k, Dinocyst sp. 2 in fig. 8a–c, Dinocyst sp. 3e–j and Dinocyst sp. 4k–o, but they did not describe them formally, although these forms have differences when compared with Deflandrea variabilis sp. nov.