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Apteodinium grande
Apteodinium grande, Cookson and Hughes, 1964
Below, 1981, considered this taxon to be a subspecies of Apteodinium maculatum Eisenack and Cookson, 1960. Lentin and Williams, 1981, retained this taxon as a species. Lucas-Clark, 1987, and Lentin and Williams, 1989, agreed with Below, 1981
Holotype: Cookson and Hughes, 1964, pl.6, fig.9; Jan du Chêne et al., 1986, pl.13, fig.5
Locus typicus: Cambridge, England
Stratum typicum: Late Albian-Early Cenomanian
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Original description: [Cookson and Hughes, 1964, p. 52]:
Description:
Shell large, almost circular in outline with a lightly defined circular girdle: epitheca with a short median solid horn which in perfect specimens narrows towards a small bifurcate tip, although sometimes as in the type, only the basal part of the horn remains. A large hoof-shaped pylome extends from the girdle to a short-distance beneath the horn. Shell membrane about 2-4 µm thick, minutely pitted, and of spongy texture.
Dimensions:
Range, overall length 111-153 µm, breadth 99-138 µm, horn 13-17 µm long, wall 2-4 µm thick.
Affinities:
Apteodinium grande is distinguishable from the German Aptian species A. granulatum Eisenack 1958 by its considerable larger size and the pitted character of its wall. It differs from the Australian Aptian-Albian species A. maculatum Eisenack and Cookson 1960 both in size and in absence of the small thickened areas with circular outlines that gives A. maculatum its characteristic appearance.
Below, 1981, considered this taxon to be a subspecies of Apteodinium maculatum Eisenack and Cookson, 1960. Lentin and Williams, 1981, retained this taxon as a species. Lucas-Clark, 1987, and Lentin and Williams, 1989, agreed with Below, 1981
Holotype: Cookson and Hughes, 1964, pl.6, fig.9; Jan du Chêne et al., 1986, pl.13, fig.5
Locus typicus: Cambridge, England
Stratum typicum: Late Albian-Early Cenomanian
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Original description: [Cookson and Hughes, 1964, p. 52]:
Description:
Shell large, almost circular in outline with a lightly defined circular girdle: epitheca with a short median solid horn which in perfect specimens narrows towards a small bifurcate tip, although sometimes as in the type, only the basal part of the horn remains. A large hoof-shaped pylome extends from the girdle to a short-distance beneath the horn. Shell membrane about 2-4 µm thick, minutely pitted, and of spongy texture.
Dimensions:
Range, overall length 111-153 µm, breadth 99-138 µm, horn 13-17 µm long, wall 2-4 µm thick.
Affinities:
Apteodinium grande is distinguishable from the German Aptian species A. granulatum Eisenack 1958 by its considerable larger size and the pitted character of its wall. It differs from the Australian Aptian-Albian species A. maculatum Eisenack and Cookson 1960 both in size and in absence of the small thickened areas with circular outlines that gives A. maculatum its characteristic appearance.