Back
Stephodinium pellucidum
From Fensome et al., 2019:
Stephodinium? pellucidum Deflandre, 1943, p.505,507; text-figs.12–16. Holotype: Deflandre, 1943, text-figs.12–13. Originally Stephodinium, subsequently (and now) Stephodinium?. Questionable assignment: Stover and Evitt (1978, p.193). Age: ?Senonian.
---------------------------------------------------------------------------------------------------
Stephodinium pellucidum n. sp. (Fig. 12 a 16.)
Holotype: AR 67. Flint (Senonian?), S.140, Saint-Leu-la-Forêt (Seine-et-Oise).
Paratype: AR .40, same provenance.
I described the characteristic of the genus Stephanodinium Defl., 1936 as the presence of a broad equatorial ridge that seems to take the place of the transverse groove. I believe it is appropriate to broaden this definition somewhat to include a new species, also possessing an equatorial formation, no longer a ridge, but simply a membranous one. Stephodinium pellucidum has an elongated ovoid cell, one of the poles being slightly ogival. Towards the widest part, a sort of annular, collar-like velum originates, apparently flexible, and is slightly directed towards one of the poles, considered in the figures as the superior pole, appears to run along the base of this velum and all around the cell. This slight annular depression could be interpreted as a transverse groove, but it is not sufficiently pronounced for straightforward identification. The cell measures 12 to 14 µm long and 7 to 8 µm wide; the total span of the velum reaches 17 to 19 µm.
The collar-like velum can, of course, be seen as an example of adaptation to planktonic life, analogous to many others that have become classic. Stephodinium pellucidum, even more so than S. coronatum, shows very clear affinities with the Gymnodinians. It is regrettable that none of the three specimens encountered so far provides a clear definition of the grooves, the presence of the transverse groove being the only probable one.
Stephodinium? pellucidum Deflandre, 1943, p.505,507; text-figs.12–16. Holotype: Deflandre, 1943, text-figs.12–13. Originally Stephodinium, subsequently (and now) Stephodinium?. Questionable assignment: Stover and Evitt (1978, p.193). Age: ?Senonian.
---------------------------------------------------------------------------------------------------
Stephodinium pellucidum n. sp. (Fig. 12 a 16.)
Holotype: AR 67. Flint (Senonian?), S.140, Saint-Leu-la-Forêt (Seine-et-Oise).
Paratype: AR .40, same provenance.
I described the characteristic of the genus Stephanodinium Defl., 1936 as the presence of a broad equatorial ridge that seems to take the place of the transverse groove. I believe it is appropriate to broaden this definition somewhat to include a new species, also possessing an equatorial formation, no longer a ridge, but simply a membranous one. Stephodinium pellucidum has an elongated ovoid cell, one of the poles being slightly ogival. Towards the widest part, a sort of annular, collar-like velum originates, apparently flexible, and is slightly directed towards one of the poles, considered in the figures as the superior pole, appears to run along the base of this velum and all around the cell. This slight annular depression could be interpreted as a transverse groove, but it is not sufficiently pronounced for straightforward identification. The cell measures 12 to 14 µm long and 7 to 8 µm wide; the total span of the velum reaches 17 to 19 µm.
The collar-like velum can, of course, be seen as an example of adaptation to planktonic life, analogous to many others that have become classic. Stephodinium pellucidum, even more so than S. coronatum, shows very clear affinities with the Gymnodinians. It is regrettable that none of the three specimens encountered so far provides a clear definition of the grooves, the presence of the transverse groove being the only probable one.