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Acanthaulax spinosissima
From Fensome et al., 2019:
Acanthaulax ?spinosissima, (Deflandre, 1939a, p. 179, ex Deflandre and Cookson, 1955, p. 258), Sarjeant, 1972, p. 22.
Holotype: Deflandre, 1939a, pl.9, fig.11.
NOW Pareodinia?.
Originally Palaeoperidinium (name not validly published), subsequently Palaeohystrichophora, thirdly Acanthaulax?, fourthly Pareodinia, fifthly (and now) Pareodinia?.
Questionable assignment: Sarjeant (1972, p.22).
Age: Late Jurassic.
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Original description: [Deflandre, 1939a, p. 179] (translated from French):
This species is known to me only from a few fragments, one of which is shown in Figure 11, PL IX. The appearance of the membrane is so characteristic that I did not believe it necessary to wait for the problematic discovery of a complete specimen in good condition to consider this organism. In a preparation stained with ruthenium red-methyl blue, the membrane is bluish and its ornamentation, formed by numerous spines, appears a beautiful purplish red. These spines, which are quite short, sometimes converge, as they seem to be able to develop quite strongly in places. Of all the species encountered in the Villers marls, this is the only one, so far, to show such a membrane. The fragment shown is 72 μ long and shows, very poorly preserved, a fairly narrow transverse groove.
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From Sarjeant, 1972:
Remarks: This species was described on the basis of fragmentary specimens from the Oxfordian of northern France and was originally placed into Palaeoperidinium, then a "waiting genus" without a specified type species and, as such, invalid under the international rules governing
biological nomenclature. It was transferred by Deflandre and Cookson (1955) to the genus Palaeohystrichophora on the basis of its possession of a general spine cover: however, subsequent studies of the type species of the latter genus, P. infusorioides Deflandre, 1935, have shown it to be a cavate cyst, which the Jurassic species certainly is not. Accordingly, Eisenack (1957) returned it to the genus Palaeoperidinium which, as
now circumscribed (Sarjeant, 1967), is an equally inappropriate placement. Subsequent to Deflandre's original description, the only observations of this species have been my own records from the Corallian (1960) and the Ampthill Clay (1962b) of Yorkshire, England. The
assignment of the English forms (which like Deflandre's original forms, were all severely damaged) to this species, originally tentative, may now be confirmed, following my examination of the holotype during visits to Prof. Deflandre's laboratory in Paris: this also shows faint traces of a tabulation, the only point of apparent difference noted in the English forms. In view of the presence of tabulation traces and the general
scatter of spines over the surface, it is here proposed that this species be provisionally reassigned to the genus Acanthaulax until such time as
better specimens can be found and the tabulation determined. Four fragmentary specimens in the upper horizon of the Upper Vardekloft Formation are assigned to this species, on the basis of general aspect, character of the spine cover, and presence of tabulation vestiges.
Acanthaulax ?spinosissima, (Deflandre, 1939a, p. 179, ex Deflandre and Cookson, 1955, p. 258), Sarjeant, 1972, p. 22.
Holotype: Deflandre, 1939a, pl.9, fig.11.
NOW Pareodinia?.
Originally Palaeoperidinium (name not validly published), subsequently Palaeohystrichophora, thirdly Acanthaulax?, fourthly Pareodinia, fifthly (and now) Pareodinia?.
Questionable assignment: Sarjeant (1972, p.22).
Age: Late Jurassic.
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Original description: [Deflandre, 1939a, p. 179] (translated from French):
This species is known to me only from a few fragments, one of which is shown in Figure 11, PL IX. The appearance of the membrane is so characteristic that I did not believe it necessary to wait for the problematic discovery of a complete specimen in good condition to consider this organism. In a preparation stained with ruthenium red-methyl blue, the membrane is bluish and its ornamentation, formed by numerous spines, appears a beautiful purplish red. These spines, which are quite short, sometimes converge, as they seem to be able to develop quite strongly in places. Of all the species encountered in the Villers marls, this is the only one, so far, to show such a membrane. The fragment shown is 72 μ long and shows, very poorly preserved, a fairly narrow transverse groove.
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From Sarjeant, 1972:
Remarks: This species was described on the basis of fragmentary specimens from the Oxfordian of northern France and was originally placed into Palaeoperidinium, then a "waiting genus" without a specified type species and, as such, invalid under the international rules governing
biological nomenclature. It was transferred by Deflandre and Cookson (1955) to the genus Palaeohystrichophora on the basis of its possession of a general spine cover: however, subsequent studies of the type species of the latter genus, P. infusorioides Deflandre, 1935, have shown it to be a cavate cyst, which the Jurassic species certainly is not. Accordingly, Eisenack (1957) returned it to the genus Palaeoperidinium which, as
now circumscribed (Sarjeant, 1967), is an equally inappropriate placement. Subsequent to Deflandre's original description, the only observations of this species have been my own records from the Corallian (1960) and the Ampthill Clay (1962b) of Yorkshire, England. The
assignment of the English forms (which like Deflandre's original forms, were all severely damaged) to this species, originally tentative, may now be confirmed, following my examination of the holotype during visits to Prof. Deflandre's laboratory in Paris: this also shows faint traces of a tabulation, the only point of apparent difference noted in the English forms. In view of the presence of tabulation traces and the general
scatter of spines over the surface, it is here proposed that this species be provisionally reassigned to the genus Acanthaulax until such time as
better specimens can be found and the tabulation determined. Four fragmentary specimens in the upper horizon of the Upper Vardekloft Formation are assigned to this species, on the basis of general aspect, character of the spine cover, and presence of tabulation vestiges.