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Raphidodinium fucatum
Raphidodinium fucatum Deflandre, 1936; emend. Sarjeant and Downie, 1982
Holotype: Deflandre, 1936, pl.10, figs.1-2,7
Locus typicus: Flint pebble, Paris, France
Stratum typicum: Upper Cretaceous (unlocalized but probably Senonian).
Age: ?Senonian
Emended diagnosis: Sarjeant and Downie 1982, p. 117-119
A species of Raphidodinium having an ovoidal to almost subpolygonal central body of relatively small size. Epitract almost hemispherical, some- what flattened apically somewhat smaller than the hypotract; the hypotract is subconical, its apex displaced slightly toward the ventral surface. Nine spines are typically developed, three surrounding the apex, four arising at or near the cingulum and two close to the antapex. The spines are acuminate and very long, their length from 14-2 times the length of the central body according to position, the shorter spines being positioned about the cingulum and the longer at the poles. Ridges or raised crests delimit a paratabulation apparently of gonyaulacoid character; the cingulum is well-marked and almost planar to feebly laevorotatory, the sulcus less well marked and of moderate breadth. Ornamentation of the phragma variable; it may be regularly to irregularly punctate and/or granulate to microvermiculate. Archaeopyle single-plate precingular (type P), formed by loss of the third precingular paraplate.
Dimensions. Holotype and paratypes; length of central body 28-30 µm, breadth 14-20 µm, length of spines 40-50 µm, total span 110-155 µm.
Stratigraphical and geographical range: Upper Cretaceous (upper Turonian-lower Maastrichtian), France, Belgium and the North Sea Basin.
Remarks: Sarjeant and Downie 1982, p. 117-119
In determining the morphology of this species, prime attention was paid to the holotype and paratypes. Under high magnification, the holotype is seen to exhibit a well-formed precingular archaeopyle on its lower surface (see Fig. 2); this specimen is almost in dorsoventral view but is slightly twisted to the left, so that the sulcus is not readily visible (and understandably escaped the attention of Prof. Deflandre). Concerning paratype AJ62, Prof. Deflandre noted in his illustration caption that ""The epitheca of this specimen appears damaged" and, whilst an archaeopyle is certainly developed, we do not consider this specimen to warrant reillustration. Paratype AJ60 is in oblique apical view; in Fig. 4, the archaeopyle may be seen at the upper centre. A specimen illustrated by Foucher shows the precingular archaeopyle with especial clarity (1971cl. pl. I fig. 10). The archaeopyle may also be visible at right in another specimen he illustrated (1971b: pl. 4 fig. 11), but we cannot be confident about this. Among the Turonian forms he cited are specimens with up to fifteen spines (Foucher 1974:126); it is probable that some of these are incorrectly attributed to this species but, unfortunately, this cannot readily be checked since no illustrations were furnished; nor were description or illustration given of the Belgian Maastrichtian forms noted by Foucher & Robaszynski ( 1977). However, the specimens seen by the second author during consulting work on North Sea cores confirm both the character of the archaeoyple and the number of spines, consistently nine. (The tenth spine sketched in Deflandre"s original figure of the holotype, on the ""southeast" side of the specimen, was found at high magnification not to be present). The situation of the spines needs to be confirmed by further research, but assuming the tabulation to be indeed gonyaulacoid, it appears to be as follows: 1. The three apical spines appear to arise at the triple junction of the crests demarcating, respectively, the second apical and first and second precingular paraplates, the second apical and second and third precingular paraplates, and the third apical and third and fourth precingular paraplates. 2. The four cingular spines appear to arise respectively at situations between the boundary separating the first and second precingular and second and third postcingular paraplates. the third and fourth postcingular and second and third precingular paraplate. the third and fourth precingular and fourth and fifth postcingular paraplate, and the fifth and sixth postcingular and precingular paraplates. 3. The two antapical spines arise slightly ventrally and probably from the triple junctions between the posterior intercalary, third postcingular and antapical paraplates and between the fifth and sixth postcingular and antapical paraplates respectively. The spines are flexuous rather than rigid, but are nevertheless sufficiently brittle to be broken on occasion (see the spine at lower right on Fig. 3a). The surface of the phragma may show regularly or irregularly spaced punctations, as originally described by Deflandre, or may exhibit a finer overall granulation, microvermiculation or punctation showing no evident pattern. This may result in part from the circumstances of fossilization and the nature of chemical treatment, if any. The specimen described as Raphidodinium cf. filcatum by de Wit (1943: 386-387, fig. 14) from the Upper Cretaceous flints of Limburg, Netherlands appears to exhibit an epitractal archaeopyle and to have intergonal, as well as gonal, spines. It is probably attributable to the genus Cauca Davey and Verdier 1971. A specimen recovered from the Upper Cretaceous of a Paris basin borehole and illustrated as Raphidodinium fucatum by Chateauneuf and Gruas-Cavagnetto (1968: pl. 8 fig. 7) appears to have a disproportionately large archaeopyle and may well also be referable to Cauca. The specimen described by Deflandre himself (1943: p. 508, pl. 17 figs. 9 and 27), as Raphidodinium fucatum forma, from the French Upper Cretaceous, has a more markedly angular central body and much shorter spines; its generic and specific allocation must for the moment be regarded as uncertain.
Holotype: Deflandre, 1936, pl.10, figs.1-2,7
Locus typicus: Flint pebble, Paris, France
Stratum typicum: Upper Cretaceous (unlocalized but probably Senonian).
Age: ?Senonian
Emended diagnosis: Sarjeant and Downie 1982, p. 117-119
A species of Raphidodinium having an ovoidal to almost subpolygonal central body of relatively small size. Epitract almost hemispherical, some- what flattened apically somewhat smaller than the hypotract; the hypotract is subconical, its apex displaced slightly toward the ventral surface. Nine spines are typically developed, three surrounding the apex, four arising at or near the cingulum and two close to the antapex. The spines are acuminate and very long, their length from 14-2 times the length of the central body according to position, the shorter spines being positioned about the cingulum and the longer at the poles. Ridges or raised crests delimit a paratabulation apparently of gonyaulacoid character; the cingulum is well-marked and almost planar to feebly laevorotatory, the sulcus less well marked and of moderate breadth. Ornamentation of the phragma variable; it may be regularly to irregularly punctate and/or granulate to microvermiculate. Archaeopyle single-plate precingular (type P), formed by loss of the third precingular paraplate.
Dimensions. Holotype and paratypes; length of central body 28-30 µm, breadth 14-20 µm, length of spines 40-50 µm, total span 110-155 µm.
Stratigraphical and geographical range: Upper Cretaceous (upper Turonian-lower Maastrichtian), France, Belgium and the North Sea Basin.
Remarks: Sarjeant and Downie 1982, p. 117-119
In determining the morphology of this species, prime attention was paid to the holotype and paratypes. Under high magnification, the holotype is seen to exhibit a well-formed precingular archaeopyle on its lower surface (see Fig. 2); this specimen is almost in dorsoventral view but is slightly twisted to the left, so that the sulcus is not readily visible (and understandably escaped the attention of Prof. Deflandre). Concerning paratype AJ62, Prof. Deflandre noted in his illustration caption that ""The epitheca of this specimen appears damaged" and, whilst an archaeopyle is certainly developed, we do not consider this specimen to warrant reillustration. Paratype AJ60 is in oblique apical view; in Fig. 4, the archaeopyle may be seen at the upper centre. A specimen illustrated by Foucher shows the precingular archaeopyle with especial clarity (1971cl. pl. I fig. 10). The archaeopyle may also be visible at right in another specimen he illustrated (1971b: pl. 4 fig. 11), but we cannot be confident about this. Among the Turonian forms he cited are specimens with up to fifteen spines (Foucher 1974:126); it is probable that some of these are incorrectly attributed to this species but, unfortunately, this cannot readily be checked since no illustrations were furnished; nor were description or illustration given of the Belgian Maastrichtian forms noted by Foucher & Robaszynski ( 1977). However, the specimens seen by the second author during consulting work on North Sea cores confirm both the character of the archaeoyple and the number of spines, consistently nine. (The tenth spine sketched in Deflandre"s original figure of the holotype, on the ""southeast" side of the specimen, was found at high magnification not to be present). The situation of the spines needs to be confirmed by further research, but assuming the tabulation to be indeed gonyaulacoid, it appears to be as follows: 1. The three apical spines appear to arise at the triple junction of the crests demarcating, respectively, the second apical and first and second precingular paraplates, the second apical and second and third precingular paraplates, and the third apical and third and fourth precingular paraplates. 2. The four cingular spines appear to arise respectively at situations between the boundary separating the first and second precingular and second and third postcingular paraplates. the third and fourth postcingular and second and third precingular paraplate. the third and fourth precingular and fourth and fifth postcingular paraplate, and the fifth and sixth postcingular and precingular paraplates. 3. The two antapical spines arise slightly ventrally and probably from the triple junctions between the posterior intercalary, third postcingular and antapical paraplates and between the fifth and sixth postcingular and antapical paraplates respectively. The spines are flexuous rather than rigid, but are nevertheless sufficiently brittle to be broken on occasion (see the spine at lower right on Fig. 3a). The surface of the phragma may show regularly or irregularly spaced punctations, as originally described by Deflandre, or may exhibit a finer overall granulation, microvermiculation or punctation showing no evident pattern. This may result in part from the circumstances of fossilization and the nature of chemical treatment, if any. The specimen described as Raphidodinium cf. filcatum by de Wit (1943: 386-387, fig. 14) from the Upper Cretaceous flints of Limburg, Netherlands appears to exhibit an epitractal archaeopyle and to have intergonal, as well as gonal, spines. It is probably attributable to the genus Cauca Davey and Verdier 1971. A specimen recovered from the Upper Cretaceous of a Paris basin borehole and illustrated as Raphidodinium fucatum by Chateauneuf and Gruas-Cavagnetto (1968: pl. 8 fig. 7) appears to have a disproportionately large archaeopyle and may well also be referable to Cauca. The specimen described by Deflandre himself (1943: p. 508, pl. 17 figs. 9 and 27), as Raphidodinium fucatum forma, from the French Upper Cretaceous, has a more markedly angular central body and much shorter spines; its generic and specific allocation must for the moment be regarded as uncertain.