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Dinogymnium heterocostatum
From Fensome et al., 2019:
Dinogymnium heterocostatum (Deflandre, 1936b, p.165–166, pl.2, fig.6) Evitt et al., 1967, p.19–20. Holotype: Deflandre, 1935,
text-fig.6; Deflandre, 1936b, pl.2, fig.6. Originally Gymnodinium (Appendix B), subsequently (and now) Dinogymnium. Age: ?Senonian.
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Original description: [Deflandre, 1936b] (translated from French):
GYMNODINIUM HETEROCOSTATUM Deflandre.
Plate II, fig. 6.
G. DEFLANDRE, Bulletin Biologique, LXIX, 1935, pp. 225, 226, fig. 6. - Les flagellates fossiles, 1936, p. 56, fig. 93.
Holotype: AF 58, Silex S. 35, pebble, Paris.
Paratype: AH 73, Senonian flint, Beynes chalk. (S.-et-O.).
The best-preserved specimen is presented in lateral view in the flake that contains it, and the longitudinal groove is located on the right (Plate II, fig. 6). As in the previous species, the epitheca and hypotheca are approximately the same size. In lateral view, as seen in the figure, the epitheca is bell-shaped and symmetrical, while the hypotheca, clearly asymmetrical, is shaped like a large cone, whose right side, adjacent to the longitudinal groove, is roughly straight. The transverse groove is narrow, but very deep. As far as can be judged by the focus, this groove is very slightly helical, and the longitudinal groove appears to develop at length on both the epitheca and the hypotheca, approaching quite close to the poles. The frontal view, which cannot be seen, but of which we can gain some knowledge by breaking it down into successive optical planes or sections using the micrometer screw, appears to be able to be described as follows: the epitheca would be conical, with a wide base and very concave sides, converging at a point towards the apex which would form a sort of carina. On the contrary, the hypotheca, bulging, would have convex sides, orienting fairly regularly towards a broadly rounded antapical pole. A subsequent examination of a specimen in oblique apical view fully confirmed this description of the epitheca. The membrane is adorned with a system of robust striations or ribs, of varying strength and length. The longest end towards the poles, and shorter ones alternate between them. In the specimen described, the long ribs of the epitheca reach the apex, while on the hypotheca, approximately one in two stops around the halfway or second third of the way down this hypotheca.
Three specimens were found in a flint pebble (? Senonian) collected in Paris. A fourth, which appears to belong to the same species, comes from a Senonian flint from the Beynes chalk (SW). In three measurable specimens, the length varies between approximately 60 and 65 μm.
The uncertainty, which cannot be completely resolved with regard to the frontal view, hardly allows for comparison with extant species. However, one can cite, as a relative, Gymnodinium diploconus Schütt (Schiller, 1932, op. cit., p. 353, fig. 359 a-c), which measures 57 to 80 μm, and whose representations, moreover, are not very concordant, present some of the characteristics of Gymnodinium heterocostatum.
But, here again, the strong striations of the membrane of the latter reject any attempt at identification between the two species.
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Comment: Evit, Clarke and Verdier 1967, p. 19-20
This species resembles D. acuminatum in important respects but, for reasons given in the discussion of that species, it is presently impossible to determine whether they are conspecific, and it seems best to treat them as distinct species. The features of the holotype, which is from a chert pebble of uncertainly Senonian age, have been thoroughly described by Deflandre and reviewed in this paper in connection with D. acuminatum. A specimen of known Senonian age, figured by Deflandre in I943, is closely similar to the holotype. The illustrations of the single specimen from the Maastrichtian of Belgium (Lejeune-Carpentier, 1951) may represent the same species but the specimen is apparently somewhat distorted, as well as being obliquely oriented in chert, so that its features can only partly be seen. The cingulum is described as showing "un certain nombre de barres transversales," features not otherwise reported for the species. The reported occurrence of specimens in the German Turonian that can be compared with this species (Alberti, 1961) is not accompanied by an illustration or description that would permit further comment on their identification. A difference in size--the German specimens being larger than the holotype--apparently explains Alberti"s use of "cf." in the specific attribution. Specific identification of the two specimens from the Senonian of Australia that were compared to this species by Deflandre and Cookson (1955) and later referred to D. westralium by Cookson and Eisenack (1958) cannot be confirmed on the basis of published information. The single published illustration does not seem to show either the pustulate surface seemingly present in the holotype of D. westralium or the granulate surface of the holotype of D. heterocostatum. The reported characteristics of size and shape do not seem adequate either to ally these specimens with one of these species, or to differentiate them from D. cretaceum as suggested by Deflandre and Cookson.
This species is also figures as (synonym list):
Gymnodinium heterocostatum DEFLANDRE, Ig3sb, Bull. Biol. France Belgique, vol. 69, p. 225-26, text-fig. 6 (nomen nudum; Senonian?, France); DEFLANDRE, Ig36a, Les Flagelles fossiles, Actual. scient. et ind., no. 335, p. 59, text-fig. 93 (nomen nudum; copy of original illustration); DEFLANDRE, Ig36b, Ann. Paleont., vol. 25, p. I65-66, pl. I2, fig. 6 (first description; copy of original illustration); DEFLANDRE, 1943, Soc. Geol. Fr., Bull., ser. 5, vol. r3, text-fig. I0 (no text; illustration of specimen from another locality; Senonian, France); LEJEUNE-CARPENTIER, 195I, Soc. Geol. Belgique, Ann., vol. 74, p. B308-30g, text-fig. 2 (Maastrichtian, Belgium); DEFLANDRE, Igs2a, Traite de Zoologie, vol. I, text-fig. 30rE (no text; copy of original figure); EISENACK, I964, Katalog der fossilen Dinoflagellaten, etc., vol. 1, p. 431-32 (with copy of original il- lustration); DOWNIE & SARJEANT, I964 (I965), Geol. Soc. America, Mem. 94, p. II6 (bibl. ref. only); G. & M. DEFLANDRE, I966, Fichier Micropaleont. Gen., ser. 15, card 2926 (no text; copies of illustrations from Deflandre, 1935, Ig36b, 1943, plus two new photomicrographs of holotype), card 2927 (no text, copy of illustration from Lejeune-Carpentier, 1951).
Dinogymnium heterocostatum (Deflandre, 1936b, p.165–166, pl.2, fig.6) Evitt et al., 1967, p.19–20. Holotype: Deflandre, 1935,
text-fig.6; Deflandre, 1936b, pl.2, fig.6. Originally Gymnodinium (Appendix B), subsequently (and now) Dinogymnium. Age: ?Senonian.
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Original description: [Deflandre, 1936b] (translated from French):
GYMNODINIUM HETEROCOSTATUM Deflandre.
Plate II, fig. 6.
G. DEFLANDRE, Bulletin Biologique, LXIX, 1935, pp. 225, 226, fig. 6. - Les flagellates fossiles, 1936, p. 56, fig. 93.
Holotype: AF 58, Silex S. 35, pebble, Paris.
Paratype: AH 73, Senonian flint, Beynes chalk. (S.-et-O.).
The best-preserved specimen is presented in lateral view in the flake that contains it, and the longitudinal groove is located on the right (Plate II, fig. 6). As in the previous species, the epitheca and hypotheca are approximately the same size. In lateral view, as seen in the figure, the epitheca is bell-shaped and symmetrical, while the hypotheca, clearly asymmetrical, is shaped like a large cone, whose right side, adjacent to the longitudinal groove, is roughly straight. The transverse groove is narrow, but very deep. As far as can be judged by the focus, this groove is very slightly helical, and the longitudinal groove appears to develop at length on both the epitheca and the hypotheca, approaching quite close to the poles. The frontal view, which cannot be seen, but of which we can gain some knowledge by breaking it down into successive optical planes or sections using the micrometer screw, appears to be able to be described as follows: the epitheca would be conical, with a wide base and very concave sides, converging at a point towards the apex which would form a sort of carina. On the contrary, the hypotheca, bulging, would have convex sides, orienting fairly regularly towards a broadly rounded antapical pole. A subsequent examination of a specimen in oblique apical view fully confirmed this description of the epitheca. The membrane is adorned with a system of robust striations or ribs, of varying strength and length. The longest end towards the poles, and shorter ones alternate between them. In the specimen described, the long ribs of the epitheca reach the apex, while on the hypotheca, approximately one in two stops around the halfway or second third of the way down this hypotheca.
Three specimens were found in a flint pebble (? Senonian) collected in Paris. A fourth, which appears to belong to the same species, comes from a Senonian flint from the Beynes chalk (SW). In three measurable specimens, the length varies between approximately 60 and 65 μm.
The uncertainty, which cannot be completely resolved with regard to the frontal view, hardly allows for comparison with extant species. However, one can cite, as a relative, Gymnodinium diploconus Schütt (Schiller, 1932, op. cit., p. 353, fig. 359 a-c), which measures 57 to 80 μm, and whose representations, moreover, are not very concordant, present some of the characteristics of Gymnodinium heterocostatum.
But, here again, the strong striations of the membrane of the latter reject any attempt at identification between the two species.
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Comment: Evit, Clarke and Verdier 1967, p. 19-20
This species resembles D. acuminatum in important respects but, for reasons given in the discussion of that species, it is presently impossible to determine whether they are conspecific, and it seems best to treat them as distinct species. The features of the holotype, which is from a chert pebble of uncertainly Senonian age, have been thoroughly described by Deflandre and reviewed in this paper in connection with D. acuminatum. A specimen of known Senonian age, figured by Deflandre in I943, is closely similar to the holotype. The illustrations of the single specimen from the Maastrichtian of Belgium (Lejeune-Carpentier, 1951) may represent the same species but the specimen is apparently somewhat distorted, as well as being obliquely oriented in chert, so that its features can only partly be seen. The cingulum is described as showing "un certain nombre de barres transversales," features not otherwise reported for the species. The reported occurrence of specimens in the German Turonian that can be compared with this species (Alberti, 1961) is not accompanied by an illustration or description that would permit further comment on their identification. A difference in size--the German specimens being larger than the holotype--apparently explains Alberti"s use of "cf." in the specific attribution. Specific identification of the two specimens from the Senonian of Australia that were compared to this species by Deflandre and Cookson (1955) and later referred to D. westralium by Cookson and Eisenack (1958) cannot be confirmed on the basis of published information. The single published illustration does not seem to show either the pustulate surface seemingly present in the holotype of D. westralium or the granulate surface of the holotype of D. heterocostatum. The reported characteristics of size and shape do not seem adequate either to ally these specimens with one of these species, or to differentiate them from D. cretaceum as suggested by Deflandre and Cookson.
This species is also figures as (synonym list):
Gymnodinium heterocostatum DEFLANDRE, Ig3sb, Bull. Biol. France Belgique, vol. 69, p. 225-26, text-fig. 6 (nomen nudum; Senonian?, France); DEFLANDRE, Ig36a, Les Flagelles fossiles, Actual. scient. et ind., no. 335, p. 59, text-fig. 93 (nomen nudum; copy of original illustration); DEFLANDRE, Ig36b, Ann. Paleont., vol. 25, p. I65-66, pl. I2, fig. 6 (first description; copy of original illustration); DEFLANDRE, 1943, Soc. Geol. Fr., Bull., ser. 5, vol. r3, text-fig. I0 (no text; illustration of specimen from another locality; Senonian, France); LEJEUNE-CARPENTIER, 195I, Soc. Geol. Belgique, Ann., vol. 74, p. B308-30g, text-fig. 2 (Maastrichtian, Belgium); DEFLANDRE, Igs2a, Traite de Zoologie, vol. I, text-fig. 30rE (no text; copy of original figure); EISENACK, I964, Katalog der fossilen Dinoflagellaten, etc., vol. 1, p. 431-32 (with copy of original il- lustration); DOWNIE & SARJEANT, I964 (I965), Geol. Soc. America, Mem. 94, p. II6 (bibl. ref. only); G. & M. DEFLANDRE, I966, Fichier Micropaleont. Gen., ser. 15, card 2926 (no text; copies of illustrations from Deflandre, 1935, Ig36b, 1943, plus two new photomicrographs of holotype), card 2927 (no text, copy of illustration from Lejeune-Carpentier, 1951).