Saitoum Pessagno, 1977

Dumitrica, Paulian & Zügel, Peter, 2003, Lower Tithonian mono- and dicyrtid Nassellaria (Radiolaria) from the Solnhofen area (southern Germany), Geodiversitas 25 (1), pp. 5-72 : 22-23

Genus Saitoum Pessagno, 1977

TYPE SPECIES. — Saitoum pagei Pessagno, 1977 ; original designation.

KNOWN RANGE. — Jurassic-Cretaceous.

REMARKS

For many monocyrtid lower Tithonian species from the material we studied in the present paper it is difficult to establish whether they belong to the genus Poulpus or to the genus Saitoum . Some of them have the arches Al rather well marked on the surface and sometimes the arch AV is weakly sketched. In other species of comparable morphology, especially when the cephalic wall is thick, these arches are not visible. As De Wever (in De Wever et al. 1979) remarked, the members of the genus Poulpus are superficially similar to Saitoum pagei , the type species of the genus Saitoum , the only difference is that the genus Poulpus has the three arches Al and AV marked as depressions on the surface of the cephalis, whereas Saitoum has no arches.

In order to better understand the differences between the two genera we also examined some specimens of S. pagei from our material and found that this species has also the three arches Al and AV. They are very weak on some segments as compared to those of Poulpus and are marked externally by three longitudinal constrictions so that the cephalis of S. pagei is three-lobate in apical view. Takemura (1986) showed also a well marked arch AV in Saitoum levium De Wever, 1981 . Therefore Poulpus could be considered a junior synonym of Saitoum . In order to preserve it we think that a better distinction between the two genera could be the presence or absence of the apical horn: the genus Poulpus could be characterized by the absence of the apical horn and Saitoum by its presence. In all the three Triassic species initially assigned to Poulpus , the type species included, the apical horn is absent. Other Triassic species assigned to this genus are also characterized by the absence of the apical horn, or when it is present it looks like a very short thorn. Saitoum , on the contrary, has always a rather well developed apical horn. A character common to both genera is also the absence of verticils of spines on feet.

Saitoum was described without a distal velum. Our well preserved material proves that a velum is almost always present, its absence being due to poor preservation.