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Evansia rotundata
(Plate IX, 1–9)
2012 Pareodinia spp. Mantle and Riding, pl. 9, figs. 5, 9
2012 Pareodinia sp. A Mantle and Riding, pl. 9, figs. 14–16 Holotype: Plate IX, 5.
Diagnosis: An intermediate-sized species of Evansia with a broad tear-shaped ambitus and a short, well-rounded apical horn. Autophragm densely granulate. Tabulation indeterminate. Archeopyle intercalary, Type?3I.
Etymology: ‘rotundata' in reference to this species broadly rounded ambitus.
Material: Palynological strew samples; 3179 m, 3206 m, 3218.55 m, 3270.78 m, Laminaria-2.
Age: Bathonian–Oxfordian (T. balmei–W. spectabilis zones; Fig. 5)
Lithostratigraphic occurrence: The Plover, Laminaria,Montara, Frigate and lower Vulcan fms of the Bonaparte Basin.
Description: An intermediate-sized, acavate, proximate dinoflagellate cystwith a broad tear-drop shape, sharply tapering into a short apical horn with a well-rounded tip. The main cyst body (excluding the apical horn) is subspherical, with an approximate aspect ratio of 5:6 (length:width). The apical horn typically accounts for 10–20% of the overall cyst length. The autophragm is irregularly granulate, typically with denser and coarser sculpture on the hypocyst. Large, arcuate folds are commonly observed on the surface of the cyst. Tabulation indicated only by the archeopyle, which is inferred to be compound intercalary, Type?3I and lacking accessory sutures.
Dimensions: (8 specimens measured)
Length including apical horn: 69 (78) 87
Length excluding apical horn: 59 (66) 78
Apical horn length: 9 (13) 18
Equatorial width: 49 (55) 64
Remarks: The questionable attribution of this species to Evansia over Pareodinia Deflandre, 1974, emend. Below, 1990 and Paraevansia Below, 1990, is based on the nature of the archeopyle. The protruding plate edge observed on the lower precingular margin, is interpreted to indicate three plate boundaries (2″–4″) and a 3I archeopyle. This assignment remains questionable, as the archeopyle tends to be poorly defined.
Comparison and remarks: Evansia? rotundata differs from E? lacryma Mantle, 2005 in being larger and having a more rounded body shape, a larger apical horn, and coarser surface ornament. The new species is wider and has a thinner autophragm than Paraevansia brachythelis Fensome, 1979 emend. Below, 1990, and lacks the apicular extension of the apical horn characteristic of that species. Evansia? rotundata differs from Paraevansia mammillata Quattrocchio and Sarjeant, 1992, in being more elongate and teardrop-shaped, and in possessing a conical, apical hornwith a broader base. Evansia alaskensis Wiggins, 1975, is distinguished by its smaller size and more accuminate apical horn. Finally, Evansia? rotundata is separated from Evansia barentsensis (Smelror, 1988) Below, 1990 in lacking a laevigate cingulum and having smaller verrucae, and from Evansia granulata Pocock, 1972, in being larger, and possessing a consistently well-rounded apical horn.
2012 Pareodinia spp. Mantle and Riding, pl. 9, figs. 5, 9
2012 Pareodinia sp. A Mantle and Riding, pl. 9, figs. 14–16 Holotype: Plate IX, 5.
Diagnosis: An intermediate-sized species of Evansia with a broad tear-shaped ambitus and a short, well-rounded apical horn. Autophragm densely granulate. Tabulation indeterminate. Archeopyle intercalary, Type?3I.
Etymology: ‘rotundata' in reference to this species broadly rounded ambitus.
Material: Palynological strew samples; 3179 m, 3206 m, 3218.55 m, 3270.78 m, Laminaria-2.
Age: Bathonian–Oxfordian (T. balmei–W. spectabilis zones; Fig. 5)
Lithostratigraphic occurrence: The Plover, Laminaria,Montara, Frigate and lower Vulcan fms of the Bonaparte Basin.
Description: An intermediate-sized, acavate, proximate dinoflagellate cystwith a broad tear-drop shape, sharply tapering into a short apical horn with a well-rounded tip. The main cyst body (excluding the apical horn) is subspherical, with an approximate aspect ratio of 5:6 (length:width). The apical horn typically accounts for 10–20% of the overall cyst length. The autophragm is irregularly granulate, typically with denser and coarser sculpture on the hypocyst. Large, arcuate folds are commonly observed on the surface of the cyst. Tabulation indicated only by the archeopyle, which is inferred to be compound intercalary, Type?3I and lacking accessory sutures.
Dimensions: (8 specimens measured)
Length including apical horn: 69 (78) 87
Length excluding apical horn: 59 (66) 78
Apical horn length: 9 (13) 18
Equatorial width: 49 (55) 64
Remarks: The questionable attribution of this species to Evansia over Pareodinia Deflandre, 1974, emend. Below, 1990 and Paraevansia Below, 1990, is based on the nature of the archeopyle. The protruding plate edge observed on the lower precingular margin, is interpreted to indicate three plate boundaries (2″–4″) and a 3I archeopyle. This assignment remains questionable, as the archeopyle tends to be poorly defined.
Comparison and remarks: Evansia? rotundata differs from E? lacryma Mantle, 2005 in being larger and having a more rounded body shape, a larger apical horn, and coarser surface ornament. The new species is wider and has a thinner autophragm than Paraevansia brachythelis Fensome, 1979 emend. Below, 1990, and lacks the apicular extension of the apical horn characteristic of that species. Evansia? rotundata differs from Paraevansia mammillata Quattrocchio and Sarjeant, 1992, in being more elongate and teardrop-shaped, and in possessing a conical, apical hornwith a broader base. Evansia alaskensis Wiggins, 1975, is distinguished by its smaller size and more accuminate apical horn. Finally, Evansia? rotundata is separated from Evansia barentsensis (Smelror, 1988) Below, 1990 in lacking a laevigate cingulum and having smaller verrucae, and from Evansia granulata Pocock, 1972, in being larger, and possessing a consistently well-rounded apical horn.