My guess is Challengeron willemoesii Haeckel. See Takahashi pl. 47 figs 6-7 in his thesis of 1981, or in the Archive section of Radiolaria.org under Takahashi 1991 (http://www.radiolaria.org/plate.htm?action=show&pi_id=580&pl_id=32).

Kjell R. Bjørklund (2008/03/17)

I think that it is either Challengeron willemoesii or Challengeron armatum. The former is in Haeckel 1887, the latter in Haecker, 1908. The photo is wonderful. Congratulations for it.

Paulian

Paulian Dumitrica (2008/03/19)

To get down to finer points, Challengeron willemoesii was described originally by Haeckel (1887) as having alternately larger and smaller spines on the margin, clearly shown on his figure. Challengeron armatum was described originally by Borgert (1901) as having short thornlike spines between the large radial spines on the margin, and his figure shows these clearly as more than one between each large spine. Takahashi (1991) figures specimens of C. willemoesii with no short spines, one short spine and several short spines between the large spines. And he synonymizes C. armatum (and other spp.) with C. willemoesii. The specimen in question here doesn’t seem to have any short spines and would fit with Takahashi’s broader concept of C. willemoesii Haeckel 1887.

-Stan

Stanley A. Kling (2008/03/21)