Back
Fromea polaris
Plate 2, figures 7–11
Derivation of name
After the ARCO North Star No. 3 well, from which the holotype and other illustrated specimens were recovered (= Polaris, the ‘North Star’).
Holotype: Plate 2, figure 7. ARCO North Star 3; 9536 ft. (core), slide 2, EF J40/1, 61.7 µm apex–antapex.
Description
Cyst with apical pylome, essentially circular in outline, often slightly skewed from apical position, usually with a thickened rim. Operculum not observed. Cyst roundly quadrate in outline, narrower toward apex. Wall moderately thick (∼2 µm), seldom folded except for commonly displaying a single longitudinal fold, either medial or offset toward the margin, suggesting an original form somewhat triangular in the polar axis.
Dimensions
51.7–61.7 (57.9 average) µm apex–antapex; 16.4–26.7 (21.0 average) µm pylome width; 41.8–63.5 (50.8 average) µm medial width (12 specimens measured).
Comment
Fromea quadrangularis Fensome et al. Citation2016, from Campanian strata in Greenland, has a similarly quadrate outline, but is much thinner, with numerous randomly oriented compression folds.
Occurrence
Rare to frequent, Hauterivian, upper Kuparuk River Formation, North Alaska.
Derivation of name
After the ARCO North Star No. 3 well, from which the holotype and other illustrated specimens were recovered (= Polaris, the ‘North Star’).
Holotype: Plate 2, figure 7. ARCO North Star 3; 9536 ft. (core), slide 2, EF J40/1, 61.7 µm apex–antapex.
Description
Cyst with apical pylome, essentially circular in outline, often slightly skewed from apical position, usually with a thickened rim. Operculum not observed. Cyst roundly quadrate in outline, narrower toward apex. Wall moderately thick (∼2 µm), seldom folded except for commonly displaying a single longitudinal fold, either medial or offset toward the margin, suggesting an original form somewhat triangular in the polar axis.
Dimensions
51.7–61.7 (57.9 average) µm apex–antapex; 16.4–26.7 (21.0 average) µm pylome width; 41.8–63.5 (50.8 average) µm medial width (12 specimens measured).
Comment
Fromea quadrangularis Fensome et al. Citation2016, from Campanian strata in Greenland, has a similarly quadrate outline, but is much thinner, with numerous randomly oriented compression folds.
Occurrence
Rare to frequent, Hauterivian, upper Kuparuk River Formation, North Alaska.