Back
Fromea nohrhansenii
Plate 3, figures 1–4
Synonymy
1993 Fromea sp. 1, Nøhr-Hansen, p. 68, pl. 9, figs 6, 7.
Derivation of name
After Dr Henrik Nøhr-Hansen of the Danish Geological Survey, who first described the form, and in recognition of his important contributions to the study of dinoflagellate cyst stratigraphy in northern regions.
Holotype Plate 3, figure 2. Pioneer Natchiq 1, 5790–5880 ft., slide 1, EF O8, 217.1 µm apex–antapex.
Description
Long slender cyst, with narrow antapex and wider apex. Cyst wall thin (∼1 µm), externally shagreenate, usually with one or two longitudinal folds extending nearly the length of the cyst. Pylome margin irregular, operculum always detached, not observed.
Dimensions
150.3–267.2 (204.0 average µm apex–antapex); 26.7–33.4 (28.9 average) µm pylome width; 36.7–46.8 (42.6 average) µm medial width (10 specimens measured).
Comments
Fromea nohrhansenii most closely resembles F. tubiformis (Martshall) comb. nov., but the latter has a conspicuous thickened rim around the pylome. Fromea nohrhansenii differs from all other species of the genus in its long, narrow form and thin, shagreenate cyst wall. Nøhr-Hansen (1993) regarded this entity as a dinoflagellate cyst.
Occurrence
Rare, Albian, Torok/Nanushuk Formations, north Alaska.
Previous record
Barremian–Albian, East Greenland (Nøhr-Hansen 1993).
Synonymy
1993 Fromea sp. 1, Nøhr-Hansen, p. 68, pl. 9, figs 6, 7.
Derivation of name
After Dr Henrik Nøhr-Hansen of the Danish Geological Survey, who first described the form, and in recognition of his important contributions to the study of dinoflagellate cyst stratigraphy in northern regions.
Holotype Plate 3, figure 2. Pioneer Natchiq 1, 5790–5880 ft., slide 1, EF O8, 217.1 µm apex–antapex.
Description
Long slender cyst, with narrow antapex and wider apex. Cyst wall thin (∼1 µm), externally shagreenate, usually with one or two longitudinal folds extending nearly the length of the cyst. Pylome margin irregular, operculum always detached, not observed.
Dimensions
150.3–267.2 (204.0 average µm apex–antapex); 26.7–33.4 (28.9 average) µm pylome width; 36.7–46.8 (42.6 average) µm medial width (10 specimens measured).
Comments
Fromea nohrhansenii most closely resembles F. tubiformis (Martshall) comb. nov., but the latter has a conspicuous thickened rim around the pylome. Fromea nohrhansenii differs from all other species of the genus in its long, narrow form and thin, shagreenate cyst wall. Nøhr-Hansen (1993) regarded this entity as a dinoflagellate cyst.
Occurrence
Rare, Albian, Torok/Nanushuk Formations, north Alaska.
Previous record
Barremian–Albian, East Greenland (Nøhr-Hansen 1993).