Your pick of the genus Aspis? might be OK, have no comments to that, but
the bug is well developed in the Norwegian Sea, site 339-11cc. Look in
Bjørklund (1976) plate 23 Figs 25-27. I had no idea about this morph back
in 1976, and I am still in the same situation. I have no more new
information on its taxonomy as I had in 1976 when I concluded: Gen. et sp.
My best age estimate of the Norwegian Sea assemblage is Middle Eocene. If
my understanding of the Paleogene distribution of rads in the north
Atlantic is correct, then the following scenario:
Rad assemblage in the north Atlantic (South of Iceland-Faeroe Ridge) has a
verry different composition than the rad assemblage in the Norwegian Sea
(north of Iceland-Faeroe Ridge). The Eocene rad fauna in the Norwegian Sea
has a stronger affinity with the faunas recovered in Siberian oil wells
(Kozlova and Gorbovetz, 1966). This make me conclude that during Eocene
there was a water connection between the Norwegian Sea and Siberia, this
probably occurred through the Arctic Ocean. The Viking Graben in the North
Sea could be an other possibility for water communication.
If you also look up in Dumitrica (1973) DSDP Leg 21, plate 3 Figs 2-4, you
will find the same guy. Paulian suggested Ceratocyrtis for the genus and
the species is unnamed.
You and Paulian have the same age on your assemblages. The age of the
Norwegian Sea assemblage arrived from the silicoflagellates and diatoms.
The Russian report on the same material in: The history of the
microplankton of the Norwegian Sea (on the Deep Sea Drilling materials)
(Explorations of the Fauna of the Seas XXII (XXXI)), 1979, also came to an
Eocene age of the oldest Norwegian Sea siliceous oozes.
There seems to be agreement on the Norwegian Sea Eocene age of this
species, so you probably have to extend its range from the Late Paleocene
to the Middle Eocene.
Kjell R. Bjørklund
Aspis murus var. from ODP 1121
Thanks for your comments. Yes, the middle Eocene specimens from Leg 38 look pretty similar. Nori Suzuki just visited here and showed me similarly similar specimens from mid Eocene of ODP leg 189. The Paleocene morphotype has a FO in NP3 at Site 208 (Dumitrica, 1973; I'm currently reviewing the rad assemblages from this site) and in NP5 at Site 1121. At both sites the FO of Aspis murus (of Nishimura, 1992, Micropal. 38: 317-362)is in NP5 followed by FO of Aspis velutochlamydosaurus (Nishimura again)in NP6-7. I'll follow up the link with the Eocene morphotype with the help of the MRC and some of Nori's material.
There appear to be a lot of similarities between the Paleogene assembalges of Leg 189 and 38.
A similar and possibly descendant species was assigned to a new genus Cymaetron by Jean-Pierre Caulet in ODP Leg 119 scientific results. The species has an Early Oligocene range.
Cymaetron sinolampas Caulet, 1991, p. 536, pl. 4, fig. 10-12.
Would seem we have the makings of an interesting high-latitude lineage, starting with Aspis described by Akiko Nishimura (1992) and possibly ending with Cymaetron.