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Palaeoperidinium spinosum

Palaeoperidinium "spinosum" Cookson and Hughes, 1964, p.49, pl.8, figs.6–8.
Holotype: Cookson and Hughes, 1964, pl.8, fig.8.
Name not validly published: generic name not validly published until 1967.
NOW Epelidosphaeridia. Originally Palaeoperidinium (name not validly published), subsequently (and now) Epelidosphaeridia.
Age: early Cenomanian.

Original diagnosis: Cookson and Hughes 1964, p. 49
Shell with convex sides, an arched apex with a slight central prominence, a slanting antapex, a shallow, circular, equatorial girdle, and a short, rather ill-defined
longitudinal furrow. A capsule is not developed. Shell-membrane thin, covered with short, blunt, hollow outgrowths c. 2 µm long which usually give the wall a scalloped appearance. The shell opens by the detachment of the distal portion of the epitheca.

Dimensions: Range: 55-67 µm long; 38-50 µm broad.

Affinities:
Cookson and Hughes, 1964, p. 49-50: The genus Palaeoperidinium has been used for this species in the general sense in which it was created by Deflandre. P.spinosum resembles P.caulleryi Deflandre (1934) in its small size, the type of its ornament, the scalloped shell outline, and the development of a slight projection on one side of the antapex. It differs, however, in having a denser ornamentation, a circular instead of helicoid girdle, and a less pronounced apical prominence. The mode of opening of the shell in P.caulleryi was not specified by Deflandre. Palaeoperidinium spinosum has not been generically associated with Spinidinium Cookson and Eisenack 1962, to the description of which it conforms in several respects, on account of its different mode of opening. In the type species S.styloniferum a pylome is present in the epitheca, in contrast to the detachment of the apex in P.spinosum.
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