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Fromea quasitabulata
Plate 2, figures 12–16
Derivation of name
From the appearance of tabulation indicated by the ridge-like ‘septa’.
Holotype: Plate 2, figure 12. Husky Walakpa 1; 2112.6 ft. (core), slide 1, EF G22/4, 50.0 µm apex–antapex.
Description
Ovoidal cyst, cylindrical, with a circular pylome in presumed apical position, slightly offset from apex in some specimens. Pylome bordered by a vaguely thickened margin, operculum not observed. Antapex rounded. Wall single-layered, smooth, relatively thin (∼1 µm), except for more or less distinct thickened ridges or folds 2–3 µm wide and high, forming a broad reticulum outlining apparent tabulation, including especially a transverse ridge in the medial position that may represent a cingular feature. The apparent tabulate geometry, although suggestive of uniformity, does not conform to known patterns of dinoflagellate cyst tabulation.
Dimensions
36.7–60.1 (46.9 average) µm apex–antapex; 11.7–20.0 (16.1 average) µm pylome width; 36.7–46.8 (42.3 average) µm medial width (12 specimens measured).
Comments
No other species ascribed to Fromea displays the tabulation-like ridges characteristic of F. quasitabulata.
Occurrence
Rare, Oxfordian, upper Kingak Formation, North Alaska.
Derivation of name
From the appearance of tabulation indicated by the ridge-like ‘septa’.
Holotype: Plate 2, figure 12. Husky Walakpa 1; 2112.6 ft. (core), slide 1, EF G22/4, 50.0 µm apex–antapex.
Description
Ovoidal cyst, cylindrical, with a circular pylome in presumed apical position, slightly offset from apex in some specimens. Pylome bordered by a vaguely thickened margin, operculum not observed. Antapex rounded. Wall single-layered, smooth, relatively thin (∼1 µm), except for more or less distinct thickened ridges or folds 2–3 µm wide and high, forming a broad reticulum outlining apparent tabulation, including especially a transverse ridge in the medial position that may represent a cingular feature. The apparent tabulate geometry, although suggestive of uniformity, does not conform to known patterns of dinoflagellate cyst tabulation.
Dimensions
36.7–60.1 (46.9 average) µm apex–antapex; 11.7–20.0 (16.1 average) µm pylome width; 36.7–46.8 (42.3 average) µm medial width (12 specimens measured).
Comments
No other species ascribed to Fromea displays the tabulation-like ridges characteristic of F. quasitabulata.
Occurrence
Rare, Oxfordian, upper Kingak Formation, North Alaska.