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Scriniodinium eurypylum
Scriniodinium eurypylum Manum and Cookson, 1964
NOW Palaeoperidinium? Originally Scriniodinium, subsequently Palaeoperidinium, thirdly Saeptodinium, fourthly (and now) Palaeoperidinium?
Holotype: Manum and Cookson, 1964, pl. 4, figs. 9-10
Locus typicus: Ellef Ringnes Island, Arctic Canada
Stratum typicum: Late Cretaceous
Original description: Manum and Cookson, 1964, p. 20-21
Shell roundish to somewhat pentagonal in outline, divided equally by a slightly laevo-rotatory girdle, and filled, almost entirely, by a capsule of circular outline whose wall is in close lateral opposition to that of the shell. The epitheca narrows gradually towards a blunt apex, usually with a short, median horn. The hypotheca, which shows clear indication of a longitudinal furrow, is usually truncate immediately below the lower limit of the capsule and usually has two inconspicuous horn-like projections of which the one on the left-hand side is the more prominent. The archeopyle is precingular, broad, extending almost to the lateral margins of the shell. The shell-membrane, less than 0.5 µm thick, is sparsely ornamented with tooth-like projections (up to 1.5 µm long) which tend to be linearly arranged, the wall of the capsule is c. 1.0 µm thick.
Dimensions: Holotype 81 x 69 µm. Range 65-81 µm long, 51-69 µm broad.
Affinities:
Manum and Cookson, 1964, p. 21: This form is rather Deflandrea-like in general appearance, however, it must be referred to Scriniodinium because of the possession of a precingular archeopyle. It does not closely resemble any of the known species of Scriniodinium and the archeopyle seems broader than is usual for this genus, particularly the sub-genus Scriniodinium Klement (1960) to which it can be referred because of the lack of a clearly-defined tabulation. However, the linear arrangement of the tooth-like processes on the shell is suggestive of some form of tabulation.
S. eurypylum resembles Deflandrea ventriosa Alberti (1959 p. 101) in size, shape, and the occurrence of a capsule that almost fills the shell. Alberti recorded the occurrence of a trapezium-shaped archeopyle in one of his 30 specimens but did not indicate whether it was intercalary, the typical position in Deflandrea or precingular. In the specimens of S. eurypylurm the position of the archeopyle has not always been evident, in others the rupture-line has been indicated while the cover is in position.
NOW Palaeoperidinium? Originally Scriniodinium, subsequently Palaeoperidinium, thirdly Saeptodinium, fourthly (and now) Palaeoperidinium?
Holotype: Manum and Cookson, 1964, pl. 4, figs. 9-10
Locus typicus: Ellef Ringnes Island, Arctic Canada
Stratum typicum: Late Cretaceous
Original description: Manum and Cookson, 1964, p. 20-21
Shell roundish to somewhat pentagonal in outline, divided equally by a slightly laevo-rotatory girdle, and filled, almost entirely, by a capsule of circular outline whose wall is in close lateral opposition to that of the shell. The epitheca narrows gradually towards a blunt apex, usually with a short, median horn. The hypotheca, which shows clear indication of a longitudinal furrow, is usually truncate immediately below the lower limit of the capsule and usually has two inconspicuous horn-like projections of which the one on the left-hand side is the more prominent. The archeopyle is precingular, broad, extending almost to the lateral margins of the shell. The shell-membrane, less than 0.5 µm thick, is sparsely ornamented with tooth-like projections (up to 1.5 µm long) which tend to be linearly arranged, the wall of the capsule is c. 1.0 µm thick.
Dimensions: Holotype 81 x 69 µm. Range 65-81 µm long, 51-69 µm broad.
Affinities:
Manum and Cookson, 1964, p. 21: This form is rather Deflandrea-like in general appearance, however, it must be referred to Scriniodinium because of the possession of a precingular archeopyle. It does not closely resemble any of the known species of Scriniodinium and the archeopyle seems broader than is usual for this genus, particularly the sub-genus Scriniodinium Klement (1960) to which it can be referred because of the lack of a clearly-defined tabulation. However, the linear arrangement of the tooth-like processes on the shell is suggestive of some form of tabulation.
S. eurypylum resembles Deflandrea ventriosa Alberti (1959 p. 101) in size, shape, and the occurrence of a capsule that almost fills the shell. Alberti recorded the occurrence of a trapezium-shaped archeopyle in one of his 30 specimens but did not indicate whether it was intercalary, the typical position in Deflandrea or precingular. In the specimens of S. eurypylurm the position of the archeopyle has not always been evident, in others the rupture-line has been indicated while the cover is in position.