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Ctenidodinium cornigerum
From Fensome et al., 2019:
Ctenidodinium cornigerum (Valensi, 1953, p.27, pl.1, figs.4,8,10; pl.2, figs.1–2; pl.13, fig.5; text-fig.2a) Jan du Chêne et al.,
1985b, p.110. Emendation: Jan du Chêne et al., 1985b, p.110, as Ctenidodinium cornigerum. Holotype: Valensi,
1953, pl.1, fig.8. Originally Gonyaulax (Appendix B), subsequently Gonyaulacysta? (combination not validly
published), thirdly Hystrichogonyaulax, fourthly (and now) Ctenidodinium. Woollam (1983, p.193) considered
Ctenidodinium combazii to be a possible taxonomic junior synonym of this species. Age: Bathonian.
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Original description: [Valensi, 1953] (as Gonyaulax cornigerum) (translated from French):
Gonyaulax cornigerum nov. sp.
PI. I, figs. 4, 8, and 10; II, figs. 1 and 2, and XIII, fig. 5; text-fig. 2 a.
HOLOTYPE: L. Valensi [1947, p. 816-818, fig. 2] (= Gonyaulax cf. cladophora) (B S 82).
PARATYPES: Bathonian, flint from Moulinet and Marnes (B S 81, B S 84). -Bathonian, flint from the cliffs between Longues and Port-en-Bessin (B S 4).
This species is quite similar to Gonyaulax cladophora DEFL., to which I had first assigned it. The shell, often globose and of identical shape, can also be more elongated with a slightly trapezoidal hypotheca and a slightly more conical epitheca; these two roughly equal parts are separated by a strongly helical transverse groove. Some specimens (Pl. II, Fig. 1) were secondarily flattened during their fossilization. The suture lines and the edges of the transverse groove bear less dense but longer and stronger processes than in Gonyaula cladophora; simple or forked, they sometimes divide near their tip into three short branches, all or only two of which may be equipped with short spines; the third is then pointed and extends the base of the process; Figures 4 and 8 (Pl. I) show the variety of forms that can be encountered. Elsewhere (Fig. 2 a), the end of the processes is capped with a conical cap, rounded or flattened, with downwardly curved edges. The processes are strongest at the intersection of the sutures with each other and with the transverse groove. I have never observed a tubular horn at the apex of the epitheca. The small number of well-preserved specimens, the rarity of ventral views, and the existence of break lines that can sometimes be confused with suture lines, make tabulation quite difficult; in the absence of clear apical and antapical views, I was unable to specify the structure of the apex and antapical; on the other hand, the first post-equatorial plate is very clear in a hypovalve viewed from the inside; The posterior part of the ventral area is sometimes separated from the longitudinal groove by a suture line.
The shell is smooth and dark brown in color.
The holotype is 55 μ long by 50 μ wide, excluding the processes, which are 10 to 15 μ; it generally varies from 50 to 80 μ long and 45 to 80 μ wide excluding the processes, and from 70 to 100 μ long by 60 to 90 μ wide including them.
It is therefore mainly in the number and size of the processes that Gonyaular cornigerum differs from Gonyaulax cladophora. Gonyaulax cornigerum is located in the Bathonian of Poitou and Normandy, but it is still much less abundant than Gonyaulax cladophora in the Bajocian.
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Emended description: [Jan du Chêne et al., 1985b] (translated from French):
Ctenidodinium cornigerum (VALENSI, 1953) comb. nov.
(Plates 1-5 and Figs. 1 and 2)
Synonymy:
1947. - Gonyaulax cf. cladophora, Valensi, p. 816-818, fig. 2.
1953. - Gonyaulax comigera, Valensi, p. 27, pl. 1, fig. 4, 8, 10; pl. 2, fig. 1, 2; pl. 13, fig. 5; text-fig. 2 a.
1969. - Hystrichogonyaulax comigera (Valensi, 1953), Sarjeant in Davey et al., p. 14.
Holotype: L. Valensi, 1953, p. 2 7; pl. 1, fig. 8;
specimen BS. 82; collection G. Deflandre, Micropaleontology Laboratory, Ecole Pratique des Hautes Etudes, National Museum of Natural History, 75005 Paris, France.
Paratypes: L. Valensi, 1953, p. 27; pl. 1, fig. 4, fig. 10; pl. 2, fig. 2; specimens BS. 81, BS. 84, BS. 4, same collection.
Emended diagnosis:
Chorate to proximochorate dinoflagellate cyst, subspherical to ellipsoidal. The hypocyst and epicyst are of approximately equal size and are separated by a strongly helical, levorotatory equatorial groove. The autophragm is thick and alveolar. This structure is reflected on the surface by punctuated ornamentation. The paratabulation is of the gonyaulacoid type 2pr, 4', 1-2a, 6", 6c, 6"', 1p, 1""', 5-6s, with the apical paraplates 2' and 4' typically separated by the preapical paraplates. This paratabulation is emphasized by low parasutural septa adorned with long, thin processes, often curved or folded. The distal end of the processes is simple or forked. It sometimes divides into three short branches, all or only two of which may be equipped with short spines, the third being pointed and a continuation of the process. Some processes are capped distally with a rounded or flattened conical cap, with downward-curved edges. The gonal processes may be stronger and longer than the intergonal processes. The latter are few in number. Their number varies from 3 to 4, rarely 5 along the longest parasutures, 1 to 2 along the shortest parasutures. They may be absent on the parasutures limiting some of the apical or sulcal paraplates. The parasutural septa are continuous and not very high. In some sutures, they may limit the antapical paraplate and the posterior part of the postcingulate plates. They limit intratabular areas with punctate ornamentation. The archaeopyle is composed of an epicystal tAtP type, with an operculum (the epicyst) that often remains attached in the sulcal area. The main suture of the archaeopyle follows the upper edge of the paracingulum. The presence of preapical and anterior intercalary paraplates cannot be demonstrated in the Valensi type material. However, these paraplates were observed in the epicysts found in field and drill samples.
Comparisons and remarks:
Ctenidodinium cornigerum (VALENSI, 1953) nov. comb. is part of a group of species common to abundant in the Bathonian layers of northwest Europe. This group also includes: Ctenidodinium omatum (EISENACK, 1935) DEFLANDRE, 1938, C. combazii DUPIN, 1968, and C. stauromatos (SARJEANT, 1976) STOVER and EVITT, 1978. These species are characterized by the presence of more or less high parasutural septa with ridges adorned with processes. These cysts are often divided at the level of the paracingulum by their epitractal archaeopyle. It therefore seems essential, in certain cases, to separate comparisons between hypocysts and epicysts. However, certain morphological characteristics remain relatively identical on both parts of the cyst: the height of the parasutural septa and the number and length of the spines or processes adorning the crest of these septa. However, it seems that, in general, the parasutures of epicysts are significantly less ornamented than those of hypocysts, particularly in Ctenidodinium combazii (DUPIN, 1968). If we refer to the original descriptions of the four aforementioned species, it appears that they correspond to four distinct types representing the extremes of morphological variations such as: size, height of parasutural septa, and number and length of spines or processes. These characteristics are the only ones that allow us to attribute a hypocyst observed in antapical view to a species.
Ctenidodinium cornigerum and C. stauromatos both possess low parasutural septa.
The size of the central body of C. comigerum appears slightly greater than that of C. stauromatos.
However, it is primarily the length of the processes, significantly greater in C. comigerum than in C. stauromatos, that differentiates these two species.
Finally, the epicyst of C. stauromatos appears to be characterized by the presence of four anterior intercalary paraplates (Sarjeant, 1976, pp. 9-10, fig. a, ... "There appear to be four anterior intercalary plates ... The number of anterior intercalary plate areas is only tentatively quoted in the diagnosis for this species" ...). The presence of these four intercalary paraplates, however, seems unlikely.
Ctenidodinium omatum and C. combazii both possess elevated parasutural septa, crowned with spines and processes that are significantly shorter than those of C. comigerum. Furthermore, Ctenidodinium combazii is distinguished by its very large size, the generally highly indented distal ends of its processes (especially its gonal processes), and the small size of its antapical paraplate 1"" relative to the size of the cyst. However, it is sometimes difficult to distinguish C. comigerum from C. ornatum. The study of certain populations, particularly specimens from the Bathonian collection at Aldorf (Gocht, 1970), shows that numerous transitional forms exist. From C. comigerum (low parasutural septa, long and few processes), we move to C. omatum by progressive elevation of the parasutural septa, reduction in the length of the processes, and increase in their number. The first indications revealing an elevation of the parasutural septa in C. comigerum are observed on the sutures limiting the antapical paraplate and the postcingulate paraplates.
Stratigraphic distribution: Valensi (1953, p. 27) attributes a Bathonian age to the holotype of the species. This author acknowledges having identified C. comigerum in the Bajocian and Bathonian of Normandy and Poitou (ibid., p. 76, tab. 5). Dupin (1965) noted numerous specimens of Gonyaulacysta comigera in its Lower Bathonian subzone IID. C. combazii is reported to be rare in this same subzone, while it accounts for nearly 90% of all dinoflagellates in Upper Bathonian subzone IIE.
Some specimens from the Aldorf Bathonian collection attributed by Gocht (1970) to the species C. ornatum undoubtedly belong to the species C. comigerum. Numerous transitional types are observable in this same collection. In their work, Fenton and Fischer (1978), Fenton et al. (1980), and Riley and Fenton (1982) included some specimens attributable to C. comigerum with those attributed to C. combazii. The distinction between the two species was certainly not made due to a lack of understanding of the transitional morphology between C. combazii and C. omatum. The paucity of precise data concerning the stratigraphic distribution of C. comigerum is certainly related to the taxonomic error in assigning this species. Indeed, authors have been able to leave in open nomenclature (Dichadogonyaulax sp., Ctenidodinium sp.) numerous specimens showing all the morphological characteristics of "Hystrichogonyaulax" comigera except the epitractal archaeopyle. Woollam (1983, pl. 1, fig. 5) attributes to Dichadogonyaulax sp. what appears to us to be a superb specimen of Ctenidodinium comigerum. According to Riding (1984, p. 201), Dichadogonyaulax sp. WOOLLAM (1983) is known from the Lower Bathonian (Zigzag Zone) to the Upper Bathonian (Aspidoides Zone?). Based on published and unpublished data (J.P.G. Fenton, pers. obs.), we can conclude that C. comigerum appears to be a characteristic species of the Tethyan realm, possibly open marine. This species becomes rare in the subboreal realm and appears absent from the boreal realm. This geographic distribution may reflect a paleolatitudinal control on the species' distribution.
Ctenidodinium cornigerum (Valensi, 1953, p.27, pl.1, figs.4,8,10; pl.2, figs.1–2; pl.13, fig.5; text-fig.2a) Jan du Chêne et al.,
1985b, p.110. Emendation: Jan du Chêne et al., 1985b, p.110, as Ctenidodinium cornigerum. Holotype: Valensi,
1953, pl.1, fig.8. Originally Gonyaulax (Appendix B), subsequently Gonyaulacysta? (combination not validly
published), thirdly Hystrichogonyaulax, fourthly (and now) Ctenidodinium. Woollam (1983, p.193) considered
Ctenidodinium combazii to be a possible taxonomic junior synonym of this species. Age: Bathonian.
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Original description: [Valensi, 1953] (as Gonyaulax cornigerum) (translated from French):
Gonyaulax cornigerum nov. sp.
PI. I, figs. 4, 8, and 10; II, figs. 1 and 2, and XIII, fig. 5; text-fig. 2 a.
HOLOTYPE: L. Valensi [1947, p. 816-818, fig. 2] (= Gonyaulax cf. cladophora) (B S 82).
PARATYPES: Bathonian, flint from Moulinet and Marnes (B S 81, B S 84). -Bathonian, flint from the cliffs between Longues and Port-en-Bessin (B S 4).
This species is quite similar to Gonyaulax cladophora DEFL., to which I had first assigned it. The shell, often globose and of identical shape, can also be more elongated with a slightly trapezoidal hypotheca and a slightly more conical epitheca; these two roughly equal parts are separated by a strongly helical transverse groove. Some specimens (Pl. II, Fig. 1) were secondarily flattened during their fossilization. The suture lines and the edges of the transverse groove bear less dense but longer and stronger processes than in Gonyaula cladophora; simple or forked, they sometimes divide near their tip into three short branches, all or only two of which may be equipped with short spines; the third is then pointed and extends the base of the process; Figures 4 and 8 (Pl. I) show the variety of forms that can be encountered. Elsewhere (Fig. 2 a), the end of the processes is capped with a conical cap, rounded or flattened, with downwardly curved edges. The processes are strongest at the intersection of the sutures with each other and with the transverse groove. I have never observed a tubular horn at the apex of the epitheca. The small number of well-preserved specimens, the rarity of ventral views, and the existence of break lines that can sometimes be confused with suture lines, make tabulation quite difficult; in the absence of clear apical and antapical views, I was unable to specify the structure of the apex and antapical; on the other hand, the first post-equatorial plate is very clear in a hypovalve viewed from the inside; The posterior part of the ventral area is sometimes separated from the longitudinal groove by a suture line.
The shell is smooth and dark brown in color.
The holotype is 55 μ long by 50 μ wide, excluding the processes, which are 10 to 15 μ; it generally varies from 50 to 80 μ long and 45 to 80 μ wide excluding the processes, and from 70 to 100 μ long by 60 to 90 μ wide including them.
It is therefore mainly in the number and size of the processes that Gonyaular cornigerum differs from Gonyaulax cladophora. Gonyaulax cornigerum is located in the Bathonian of Poitou and Normandy, but it is still much less abundant than Gonyaulax cladophora in the Bajocian.
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Emended description: [Jan du Chêne et al., 1985b] (translated from French):
Ctenidodinium cornigerum (VALENSI, 1953) comb. nov.
(Plates 1-5 and Figs. 1 and 2)
Synonymy:
1947. - Gonyaulax cf. cladophora, Valensi, p. 816-818, fig. 2.
1953. - Gonyaulax comigera, Valensi, p. 27, pl. 1, fig. 4, 8, 10; pl. 2, fig. 1, 2; pl. 13, fig. 5; text-fig. 2 a.
1969. - Hystrichogonyaulax comigera (Valensi, 1953), Sarjeant in Davey et al., p. 14.
Holotype: L. Valensi, 1953, p. 2 7; pl. 1, fig. 8;
specimen BS. 82; collection G. Deflandre, Micropaleontology Laboratory, Ecole Pratique des Hautes Etudes, National Museum of Natural History, 75005 Paris, France.
Paratypes: L. Valensi, 1953, p. 27; pl. 1, fig. 4, fig. 10; pl. 2, fig. 2; specimens BS. 81, BS. 84, BS. 4, same collection.
Emended diagnosis:
Chorate to proximochorate dinoflagellate cyst, subspherical to ellipsoidal. The hypocyst and epicyst are of approximately equal size and are separated by a strongly helical, levorotatory equatorial groove. The autophragm is thick and alveolar. This structure is reflected on the surface by punctuated ornamentation. The paratabulation is of the gonyaulacoid type 2pr, 4', 1-2a, 6", 6c, 6"', 1p, 1""', 5-6s, with the apical paraplates 2' and 4' typically separated by the preapical paraplates. This paratabulation is emphasized by low parasutural septa adorned with long, thin processes, often curved or folded. The distal end of the processes is simple or forked. It sometimes divides into three short branches, all or only two of which may be equipped with short spines, the third being pointed and a continuation of the process. Some processes are capped distally with a rounded or flattened conical cap, with downward-curved edges. The gonal processes may be stronger and longer than the intergonal processes. The latter are few in number. Their number varies from 3 to 4, rarely 5 along the longest parasutures, 1 to 2 along the shortest parasutures. They may be absent on the parasutures limiting some of the apical or sulcal paraplates. The parasutural septa are continuous and not very high. In some sutures, they may limit the antapical paraplate and the posterior part of the postcingulate plates. They limit intratabular areas with punctate ornamentation. The archaeopyle is composed of an epicystal tAtP type, with an operculum (the epicyst) that often remains attached in the sulcal area. The main suture of the archaeopyle follows the upper edge of the paracingulum. The presence of preapical and anterior intercalary paraplates cannot be demonstrated in the Valensi type material. However, these paraplates were observed in the epicysts found in field and drill samples.
Comparisons and remarks:
Ctenidodinium cornigerum (VALENSI, 1953) nov. comb. is part of a group of species common to abundant in the Bathonian layers of northwest Europe. This group also includes: Ctenidodinium omatum (EISENACK, 1935) DEFLANDRE, 1938, C. combazii DUPIN, 1968, and C. stauromatos (SARJEANT, 1976) STOVER and EVITT, 1978. These species are characterized by the presence of more or less high parasutural septa with ridges adorned with processes. These cysts are often divided at the level of the paracingulum by their epitractal archaeopyle. It therefore seems essential, in certain cases, to separate comparisons between hypocysts and epicysts. However, certain morphological characteristics remain relatively identical on both parts of the cyst: the height of the parasutural septa and the number and length of the spines or processes adorning the crest of these septa. However, it seems that, in general, the parasutures of epicysts are significantly less ornamented than those of hypocysts, particularly in Ctenidodinium combazii (DUPIN, 1968). If we refer to the original descriptions of the four aforementioned species, it appears that they correspond to four distinct types representing the extremes of morphological variations such as: size, height of parasutural septa, and number and length of spines or processes. These characteristics are the only ones that allow us to attribute a hypocyst observed in antapical view to a species.
Ctenidodinium cornigerum and C. stauromatos both possess low parasutural septa.
The size of the central body of C. comigerum appears slightly greater than that of C. stauromatos.
However, it is primarily the length of the processes, significantly greater in C. comigerum than in C. stauromatos, that differentiates these two species.
Finally, the epicyst of C. stauromatos appears to be characterized by the presence of four anterior intercalary paraplates (Sarjeant, 1976, pp. 9-10, fig. a, ... "There appear to be four anterior intercalary plates ... The number of anterior intercalary plate areas is only tentatively quoted in the diagnosis for this species" ...). The presence of these four intercalary paraplates, however, seems unlikely.
Ctenidodinium omatum and C. combazii both possess elevated parasutural septa, crowned with spines and processes that are significantly shorter than those of C. comigerum. Furthermore, Ctenidodinium combazii is distinguished by its very large size, the generally highly indented distal ends of its processes (especially its gonal processes), and the small size of its antapical paraplate 1"" relative to the size of the cyst. However, it is sometimes difficult to distinguish C. comigerum from C. ornatum. The study of certain populations, particularly specimens from the Bathonian collection at Aldorf (Gocht, 1970), shows that numerous transitional forms exist. From C. comigerum (low parasutural septa, long and few processes), we move to C. omatum by progressive elevation of the parasutural septa, reduction in the length of the processes, and increase in their number. The first indications revealing an elevation of the parasutural septa in C. comigerum are observed on the sutures limiting the antapical paraplate and the postcingulate paraplates.
Stratigraphic distribution: Valensi (1953, p. 27) attributes a Bathonian age to the holotype of the species. This author acknowledges having identified C. comigerum in the Bajocian and Bathonian of Normandy and Poitou (ibid., p. 76, tab. 5). Dupin (1965) noted numerous specimens of Gonyaulacysta comigera in its Lower Bathonian subzone IID. C. combazii is reported to be rare in this same subzone, while it accounts for nearly 90% of all dinoflagellates in Upper Bathonian subzone IIE.
Some specimens from the Aldorf Bathonian collection attributed by Gocht (1970) to the species C. ornatum undoubtedly belong to the species C. comigerum. Numerous transitional types are observable in this same collection. In their work, Fenton and Fischer (1978), Fenton et al. (1980), and Riley and Fenton (1982) included some specimens attributable to C. comigerum with those attributed to C. combazii. The distinction between the two species was certainly not made due to a lack of understanding of the transitional morphology between C. combazii and C. omatum. The paucity of precise data concerning the stratigraphic distribution of C. comigerum is certainly related to the taxonomic error in assigning this species. Indeed, authors have been able to leave in open nomenclature (Dichadogonyaulax sp., Ctenidodinium sp.) numerous specimens showing all the morphological characteristics of "Hystrichogonyaulax" comigera except the epitractal archaeopyle. Woollam (1983, pl. 1, fig. 5) attributes to Dichadogonyaulax sp. what appears to us to be a superb specimen of Ctenidodinium comigerum. According to Riding (1984, p. 201), Dichadogonyaulax sp. WOOLLAM (1983) is known from the Lower Bathonian (Zigzag Zone) to the Upper Bathonian (Aspidoides Zone?). Based on published and unpublished data (J.P.G. Fenton, pers. obs.), we can conclude that C. comigerum appears to be a characteristic species of the Tethyan realm, possibly open marine. This species becomes rare in the subboreal realm and appears absent from the boreal realm. This geographic distribution may reflect a paleolatitudinal control on the species' distribution.