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Dinogymnium laticinctum
Dinogymnium laticinctum (Deflandre, 1943) Evitt et al., 1967
Originally Gymnodinium, subsequently (and now) Dinogymnium.
The transfer of this species to Dinogymnium is not attributable to Boltenhagen, 1977.
Holotype: Deflandre, 1943, pl.17, fig.3; text-fig.11
Age: ?Senonian
Original description, Deflandre, 1943: Gymnodinium laticinctum n.sp. (Fig. 11 et Pl. XVII, fig. 3) translation PKB 2025:
Holotype : AF 45. Silex ( ? Senonien S.35, Paris.
The type, unique, is deformed quite notably, but it has retained very particular characteristics allowing to differentiate it from the known species. The cell seems to have undergone a deformation similar to that presented by a rubber balloon that is evacuated. The anterior wall in the drawing fig. 11, is partially concave and pushed back towards the opposite face. It is also difficult to define the exact orientation of the organism which, I believe, is presented in oblique right lateral view: the longitudinal groove would therefore be found on the left of the drawing. The epitheca is slightly larger than the hypotheca and both have a largely rounded pole; the general outline is substantially ellipsoidal. The most striking characteristic lies in the large relative width of the transverse groove, which exceeds a seventh of the total length (about 15%). It should be noted, in this regard, that the general deformations undergone by the cell have not affected this character of the transverse furrow, as can be judged from the left part of the drawing. The membrane bears longitudinal striations, spaced from each other, at their origin on the transverse furrow, of approximately 2 µm to 2.5 µm. There should have been at most twenty perceptible in frontal view. The cell, as it appears, measures 57 µm long by approximately 37 µm wide.
Gymnodinium laticinetum is not related to any currently known fossil Gymnodinium. The only species that can be compared to it is Gymnodinium radiatum Kofoid and Swezy from the recent plankton of the Californian coasts of the Pacific Ocean. The relationship between the two species is clearly marked, taking into account the deformations undergone by the fossil species. The two forms, however, are separated from each other: 1° by the number of striae, which are much tighter in G. radiatum (about 50 striae, in ventral view); 2° by the relative width of the furrow (9.4% of the total length in G. radiatum); 3° finally by the clearly superior dimensions of the current species (length 86 μ). It is, however, interesting to note that, among the Gymnodinium of the present seas, G. radiatum is one of those which possesses the widest transverse furrow in proportion to the length. Gymnodinium laticinctum comes from a flint, probably Senonian, collected in Paris, in which two other species of Gymnodinium (G. heterocostatum DEFL. and G. digitus DEFL;) have already been described.
Originally Gymnodinium, subsequently (and now) Dinogymnium.
The transfer of this species to Dinogymnium is not attributable to Boltenhagen, 1977.
Holotype: Deflandre, 1943, pl.17, fig.3; text-fig.11
Age: ?Senonian
Original description, Deflandre, 1943: Gymnodinium laticinctum n.sp. (Fig. 11 et Pl. XVII, fig. 3) translation PKB 2025:
Holotype : AF 45. Silex ( ? Senonien S.35, Paris.
The type, unique, is deformed quite notably, but it has retained very particular characteristics allowing to differentiate it from the known species. The cell seems to have undergone a deformation similar to that presented by a rubber balloon that is evacuated. The anterior wall in the drawing fig. 11, is partially concave and pushed back towards the opposite face. It is also difficult to define the exact orientation of the organism which, I believe, is presented in oblique right lateral view: the longitudinal groove would therefore be found on the left of the drawing. The epitheca is slightly larger than the hypotheca and both have a largely rounded pole; the general outline is substantially ellipsoidal. The most striking characteristic lies in the large relative width of the transverse groove, which exceeds a seventh of the total length (about 15%). It should be noted, in this regard, that the general deformations undergone by the cell have not affected this character of the transverse furrow, as can be judged from the left part of the drawing. The membrane bears longitudinal striations, spaced from each other, at their origin on the transverse furrow, of approximately 2 µm to 2.5 µm. There should have been at most twenty perceptible in frontal view. The cell, as it appears, measures 57 µm long by approximately 37 µm wide.
Gymnodinium laticinetum is not related to any currently known fossil Gymnodinium. The only species that can be compared to it is Gymnodinium radiatum Kofoid and Swezy from the recent plankton of the Californian coasts of the Pacific Ocean. The relationship between the two species is clearly marked, taking into account the deformations undergone by the fossil species. The two forms, however, are separated from each other: 1° by the number of striae, which are much tighter in G. radiatum (about 50 striae, in ventral view); 2° by the relative width of the furrow (9.4% of the total length in G. radiatum); 3° finally by the clearly superior dimensions of the current species (length 86 μ). It is, however, interesting to note that, among the Gymnodinium of the present seas, G. radiatum is one of those which possesses the widest transverse furrow in proportion to the length. Gymnodinium laticinctum comes from a flint, probably Senonian, collected in Paris, in which two other species of Gymnodinium (G. heterocostatum DEFL. and G. digitus DEFL;) have already been described.