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Volkheimeridium lanterna
From Fensome et al., 2019:
Volkheimeridium lanterna (Cookson and Eisenack, 1970a, p.144–145, pl.12, figs.1–3) Quattrocchio and Sarjeant, 2003, p.136.
Holotype: Cookson and Eisenack, 1970a, pl.12, fig.2.
NOW Spinidinium. Originally (and now) Spinidinium, subsequently Volkheimeridium.
NIA. Age: Late Cretaceous.
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Original description: Cookson and Eisenack, 1970, p.144
Shell somewhat biconical, clearly divided by a relatively conspicuous girdle into a longer epitheca with straight to slightly convex slanting sides and a short apical horn and a shorter, somewhat broader hypotheca with slanting, slightly convex sides and a narrow, pointed antapical horn to one side of the midline. The girdle is relatively broad, interrupted laterally on the dorsal surface, its ends on the ventral surface being rather widely separated.
The tabulation, which is most evident in the epitheca, is difficult to determine. The plates appear to be long, narrow and triangular in outline and to extend from the girdle to near the apex. There seem to be six precingular plates in the epitheca; the number in the hypotheca has not been determined. However, in several specimens, a small semicircular area, outlined by a single row of small, evenly-spaced thickenings, which extends between the two lateral breaks in the girdle, has been evident on the dorsal surface of the hypotheca (Pl. 12, fig. 2).
The outlines of both the shell and plates are ornamented with distinctly pointed spines which vary somewhat, both in size and density, in individual specimens. The archeopyle is small, intercalary and high in the epitheca. The internal body is large, thin and smooth-walled and, except at the extreme apex, almost fills the shell.
Dimensions: based on 20 examples: Holotype: length c. 70 µm, breadth 50 µm. Range: c. 55-78 µm long, 37-57 µm broad.
Affinities:
Cookson and Eisenack, 1970, p.144: Although the outer wall of Spinidinium lanterna is clearly tabulated and the species not uncommon, it has not been possible to determine the exact tabulation. The main features by which S. Ianterna can be distinguished from S. stylonifera Cookson and Eisenack 1962 from Western and South Australian Aptian and Albian deposits are: the greater difference between the lengths of the epitheca and hypotheca, straighter sides, clearer tabulation, longer and more clearly outlined triangular plates and the finer type of ornamentation.
Volkheimeridium lanterna (Cookson and Eisenack, 1970a, p.144–145, pl.12, figs.1–3) Quattrocchio and Sarjeant, 2003, p.136.
Holotype: Cookson and Eisenack, 1970a, pl.12, fig.2.
NOW Spinidinium. Originally (and now) Spinidinium, subsequently Volkheimeridium.
NIA. Age: Late Cretaceous.
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Original description: Cookson and Eisenack, 1970, p.144
Shell somewhat biconical, clearly divided by a relatively conspicuous girdle into a longer epitheca with straight to slightly convex slanting sides and a short apical horn and a shorter, somewhat broader hypotheca with slanting, slightly convex sides and a narrow, pointed antapical horn to one side of the midline. The girdle is relatively broad, interrupted laterally on the dorsal surface, its ends on the ventral surface being rather widely separated.
The tabulation, which is most evident in the epitheca, is difficult to determine. The plates appear to be long, narrow and triangular in outline and to extend from the girdle to near the apex. There seem to be six precingular plates in the epitheca; the number in the hypotheca has not been determined. However, in several specimens, a small semicircular area, outlined by a single row of small, evenly-spaced thickenings, which extends between the two lateral breaks in the girdle, has been evident on the dorsal surface of the hypotheca (Pl. 12, fig. 2).
The outlines of both the shell and plates are ornamented with distinctly pointed spines which vary somewhat, both in size and density, in individual specimens. The archeopyle is small, intercalary and high in the epitheca. The internal body is large, thin and smooth-walled and, except at the extreme apex, almost fills the shell.
Dimensions: based on 20 examples: Holotype: length c. 70 µm, breadth 50 µm. Range: c. 55-78 µm long, 37-57 µm broad.
Affinities:
Cookson and Eisenack, 1970, p.144: Although the outer wall of Spinidinium lanterna is clearly tabulated and the species not uncommon, it has not been possible to determine the exact tabulation. The main features by which S. Ianterna can be distinguished from S. stylonifera Cookson and Eisenack 1962 from Western and South Australian Aptian and Albian deposits are: the greater difference between the lengths of the epitheca and hypotheca, straighter sides, clearer tabulation, longer and more clearly outlined triangular plates and the finer type of ornamentation.