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Apectodinium geometricum
From Fensome et al., 2019:
Apectodinium geometricum, (Pastiels, 1948, p.41, pl.4, figs.1–11 ex Downie and Sarjeant, 1965, p.90) Fensome et al., 1990, p.617.
Holotype: Pastiels, 1948, pl.4, fig.4.
Originally Hystrichosphaeridium geometricum (name illegitimate), subsequently Baltisphaeridium geometricum (Appendix A), thirdly Apectodinium pastielsii (name illegitimate), fourthly Apectodinium geometricum.
Nomenclatural junior synonym: Apectodinium pastielsii, which has the same type.
Taxonomic junior synonym (at specific rank): Wetzeliella homomorpha var. quinquelata (as Wetzeliella quinquelata, now Apectodinium quinquelatum), by implication in Harland (1979c, p.67), who considered the latter to be the senior name — however, Lentin and Williams (1989, p.18) retained Apectodinium quinquelatum.
The name Hystrichosphaeridium geometricum Pastiels is an illegitimate junior homonym of Hystrichosphaeridium geometricum Deflandre, 1945a. By "transferring" Pastiels' species to Baltisphaeridium, Downie and Sarjeant (1965, p.90) created the valid and legitimate name Baltisphaeridium geometricum Pastiels, 1948 ex Downie and Sarjeant, 1965. The name Apectodinium pastielsii Lentin and Williams, 1989, is thus superfluous. Deflandre and Cookson (1955, p.254) identified the specimen illustrated in Pastiels (1948, pl.4, fig.8) as Wetzeliella (now Apectodinium) homomorpha.
Age: Ypresian.
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Original description: [Pastiels, 1948] (translated from French):
Hystrichosphaeridium geometricum nov. sp.
(Pl. IV, figs. 1 to 11.)
Holotype: Pl. IV, fig. 4.
Paratypes: Pl. IV, figs. 6, 7, and 8.
G. DEFLANDRE has grouped under the name H. multifurcatum, a collective species, "all Hystrichosphaerids bristling with numerous forked appendages, whose height does not exceed a quarter of the diameter of the cell and is often much smaller." I propose to use the terms of this definition to apply them, and restrict them, to non-spherical, capsular Hystrichosphaerids, often with a polygonal outline, and to group these under the name Hystrichosphaeridium geometricum.
DIAGNOSIS:
The shell of Hystrichosphaeridium geometricum is a lenticular capsule with a more or less regular polygonal outline and a smooth integument, adorned with appendages. The processes are mostly spiny or tubular, often forked, sometimes divided and distributed irregularly on the shells by small ridges. The diameter of the cell varies from approximately 40 to 60 microns; the length of the appendages is 10 to 20 microns, and the thickness of the central capsule is around 10 to 15 microns. The species is very polymorphic.
In the Ypresian plankton, this new species is represented by flattened, roughly pentagonal capsules, with one side, sometimes concave, being smaller. The appendages, which are very numerous, are particularly numerous at the edge of the capsule. Of highly variable types, they are composed of either short, truncated or tubular spines or short, branched appendages of varying size.
At the corners of the polygon, and particularly at the ends of the short side, two stubby, polyfid processes are visible, larger than the others;
on the surface of the capsule, short ridges for the insertion of the appendages. The surface of the shell, colorless and transparent, is smooth. Cell diameter: 50 to 60 microns; appendage length: 5 to 15 microns; total span: 60 to 90 microns.
HARVESTING SITES:
Quenast, Blorquiau Quarry, lower and upper clay banks; Ghent, artesian well.
Apectodinium geometricum, (Pastiels, 1948, p.41, pl.4, figs.1–11 ex Downie and Sarjeant, 1965, p.90) Fensome et al., 1990, p.617.
Holotype: Pastiels, 1948, pl.4, fig.4.
Originally Hystrichosphaeridium geometricum (name illegitimate), subsequently Baltisphaeridium geometricum (Appendix A), thirdly Apectodinium pastielsii (name illegitimate), fourthly Apectodinium geometricum.
Nomenclatural junior synonym: Apectodinium pastielsii, which has the same type.
Taxonomic junior synonym (at specific rank): Wetzeliella homomorpha var. quinquelata (as Wetzeliella quinquelata, now Apectodinium quinquelatum), by implication in Harland (1979c, p.67), who considered the latter to be the senior name — however, Lentin and Williams (1989, p.18) retained Apectodinium quinquelatum.
The name Hystrichosphaeridium geometricum Pastiels is an illegitimate junior homonym of Hystrichosphaeridium geometricum Deflandre, 1945a. By "transferring" Pastiels' species to Baltisphaeridium, Downie and Sarjeant (1965, p.90) created the valid and legitimate name Baltisphaeridium geometricum Pastiels, 1948 ex Downie and Sarjeant, 1965. The name Apectodinium pastielsii Lentin and Williams, 1989, is thus superfluous. Deflandre and Cookson (1955, p.254) identified the specimen illustrated in Pastiels (1948, pl.4, fig.8) as Wetzeliella (now Apectodinium) homomorpha.
Age: Ypresian.
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Original description: [Pastiels, 1948] (translated from French):
Hystrichosphaeridium geometricum nov. sp.
(Pl. IV, figs. 1 to 11.)
Holotype: Pl. IV, fig. 4.
Paratypes: Pl. IV, figs. 6, 7, and 8.
G. DEFLANDRE has grouped under the name H. multifurcatum, a collective species, "all Hystrichosphaerids bristling with numerous forked appendages, whose height does not exceed a quarter of the diameter of the cell and is often much smaller." I propose to use the terms of this definition to apply them, and restrict them, to non-spherical, capsular Hystrichosphaerids, often with a polygonal outline, and to group these under the name Hystrichosphaeridium geometricum.
DIAGNOSIS:
The shell of Hystrichosphaeridium geometricum is a lenticular capsule with a more or less regular polygonal outline and a smooth integument, adorned with appendages. The processes are mostly spiny or tubular, often forked, sometimes divided and distributed irregularly on the shells by small ridges. The diameter of the cell varies from approximately 40 to 60 microns; the length of the appendages is 10 to 20 microns, and the thickness of the central capsule is around 10 to 15 microns. The species is very polymorphic.
In the Ypresian plankton, this new species is represented by flattened, roughly pentagonal capsules, with one side, sometimes concave, being smaller. The appendages, which are very numerous, are particularly numerous at the edge of the capsule. Of highly variable types, they are composed of either short, truncated or tubular spines or short, branched appendages of varying size.
At the corners of the polygon, and particularly at the ends of the short side, two stubby, polyfid processes are visible, larger than the others;
on the surface of the capsule, short ridges for the insertion of the appendages. The surface of the shell, colorless and transparent, is smooth. Cell diameter: 50 to 60 microns; appendage length: 5 to 15 microns; total span: 60 to 90 microns.
HARVESTING SITES:
Quenast, Blorquiau Quarry, lower and upper clay banks; Ghent, artesian well.