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Phanerodinium setiferum
From Fensome et al., 2019:
Phanerodinium setiferum Deflandre, 1937a, p.112–114; text-fig.5. Holotype: Deflandre, 1937a, text-fig.5. Age: Senonian.
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Original description, Deflandre, 1937: Translation PKB 2025:
The general shape of the theca is similar to that of P. cayeuxi: the epitheca is about three times larger than the hypotheca. The transverse groove is apparently circular, but, as in P. cayeuxi, the longitudinal groove has not been recognized. It is true that I still only have two specimens of P. setiferum to contrast with about thirty P. cayeuxi. P. setiferum, and this is its specific characteristic, is adorned with long, slender setae, or if you like, needles, which are all located at the angles of the plates: no needle originates on the surface of the latter. There are thus setae at all angles, both at those made between the plates and at those made with the transverse groove. Moreover, the latter being made of plates, needles also originate at their junction points. The tabulation of P. setiferum could not be established, nor could the presence of the characteristic elongated plate located against the apical plate. But this is due to the poor orientation of my samples. The length of the theca is about 18.5 μ and its width 16 μ. The setae, some stiff, others more or less curved, measure from 5 to 7.5 μ.
Phanerodinium setiferum, very well characterized by the presence of setae, is however close to P. cayeuxi. Indeed, it sometimes happens, in this species that we find, at the location where the setae of P. setiferum are, very short spines. But, out of thirty specimens of P. cayeuxi, found in ten different flints and from varied sources, none presents true setae, and the homogeneity of their physiognomy allows us to conclude that it is a true type, clearly separated from P. setiferum. It is not without interest to note, in this new Dinoflagellate, the particular situation of the setae which originate in conditions quite similar to those of Hystrichosphaera. Let us recall that on the contrary, in Dinoflagellates like Cladopyxis, the prominent ornaments (horns, forked processes) originate on the very surface of the plates and not at the angles, which is essentially different. Since we are discussing the genus Cladopyxis, let us note that, in his revision of the Dinoflagella (Rabenhorst's Kryptogamenflora, Bd. X, Abt. 3), J. SCHILLER gave figures of two very small forms, Cladopyxis setifera Lohmann and Cl. bacillifera Schiller. These two species have a certain kinship in appearance with our P. setiferum, as well as with the Raphidodinium fucatum that I described in 1936.
But, besides secondary questions of dimensions, the species of Lohmann and Schiller are slender and do not seem to show any trace of tabulation. Thus, there is no serious connection to be made with my species of flints. Moreover, it must also be noted that the position of Cladopyxis setifera and bacillifera within the genus Cladopyxis is somewhat artificial and open to criticism. This genus Cladopyxis is perfectly delimited at present and its tabulation established (1). It is therefore only as a result of the presence of special ornaments (long, pointed spines in C. setifera, bacillary in C. bacillifera) that Lohmann and, after him, Schiller, placed these two small forms in the genus Cladopyxis. The latter is, in fact, the only one among the Dinoflagellates to present such a system of ornamentation. It would be much better, in my opinion, to place these two small nanoplankton Dinoflagellates in a special genus, and I propose the name: Micracanthodinium n. g.
Phanerodinium setiferum Deflandre, 1937a, p.112–114; text-fig.5. Holotype: Deflandre, 1937a, text-fig.5. Age: Senonian.
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Original description, Deflandre, 1937: Translation PKB 2025:
The general shape of the theca is similar to that of P. cayeuxi: the epitheca is about three times larger than the hypotheca. The transverse groove is apparently circular, but, as in P. cayeuxi, the longitudinal groove has not been recognized. It is true that I still only have two specimens of P. setiferum to contrast with about thirty P. cayeuxi. P. setiferum, and this is its specific characteristic, is adorned with long, slender setae, or if you like, needles, which are all located at the angles of the plates: no needle originates on the surface of the latter. There are thus setae at all angles, both at those made between the plates and at those made with the transverse groove. Moreover, the latter being made of plates, needles also originate at their junction points. The tabulation of P. setiferum could not be established, nor could the presence of the characteristic elongated plate located against the apical plate. But this is due to the poor orientation of my samples. The length of the theca is about 18.5 μ and its width 16 μ. The setae, some stiff, others more or less curved, measure from 5 to 7.5 μ.
Phanerodinium setiferum, very well characterized by the presence of setae, is however close to P. cayeuxi. Indeed, it sometimes happens, in this species that we find, at the location where the setae of P. setiferum are, very short spines. But, out of thirty specimens of P. cayeuxi, found in ten different flints and from varied sources, none presents true setae, and the homogeneity of their physiognomy allows us to conclude that it is a true type, clearly separated from P. setiferum. It is not without interest to note, in this new Dinoflagellate, the particular situation of the setae which originate in conditions quite similar to those of Hystrichosphaera. Let us recall that on the contrary, in Dinoflagellates like Cladopyxis, the prominent ornaments (horns, forked processes) originate on the very surface of the plates and not at the angles, which is essentially different. Since we are discussing the genus Cladopyxis, let us note that, in his revision of the Dinoflagella (Rabenhorst's Kryptogamenflora, Bd. X, Abt. 3), J. SCHILLER gave figures of two very small forms, Cladopyxis setifera Lohmann and Cl. bacillifera Schiller. These two species have a certain kinship in appearance with our P. setiferum, as well as with the Raphidodinium fucatum that I described in 1936.
But, besides secondary questions of dimensions, the species of Lohmann and Schiller are slender and do not seem to show any trace of tabulation. Thus, there is no serious connection to be made with my species of flints. Moreover, it must also be noted that the position of Cladopyxis setifera and bacillifera within the genus Cladopyxis is somewhat artificial and open to criticism. This genus Cladopyxis is perfectly delimited at present and its tabulation established (1). It is therefore only as a result of the presence of special ornaments (long, pointed spines in C. setifera, bacillary in C. bacillifera) that Lohmann and, after him, Schiller, placed these two small forms in the genus Cladopyxis. The latter is, in fact, the only one among the Dinoflagellates to present such a system of ornamentation. It would be much better, in my opinion, to place these two small nanoplankton Dinoflagellates in a special genus, and I propose the name: Micracanthodinium n. g.