Haeckel, 1881
Solitary or colonial polycystines without a siliceous skeleton, or provided with simple or branched spicules scattered in the calymma. According to Haeckel (1887), this group comprises 4 families: Family Thalassicollida, Family Collozoida, Family Thalassosphaerida, and Family Phaerozoida.
Due to their fragility, members of this group preserve poorly in net plankton samples, and either do not preserve at all or are represented only by their spicules in sedimentary materials. Partly because of these limitations, information on their classification and distribution is extremely scarce, and no further details are given on this group in this chapter. Detailed reviews of the colonial radiolarians, including several Collodaria, were produced by Hollande and Enjumet (1953), Strelkov and Reshetnjak (1971), and Swanberg (1979).
Most of these species have tropical distribution ranges in the three major oceans. In the south Atlantic they are probably restricted to waters associated with the equatorial current system, the Tropics/Subtropics, and the oligotrophic Central Gyre (main biogeographic areas).
The order comprises four families:
Family Thalassicollida (solitary, no skeletal elements)
Family Collozoida (colonial, no skeletal elements)
Family Thalassosphaerida (solitary, with siliceous spicules scattered in the calymna)
Family Sphaerozoida (colonial, with siliceous spicules scattered in the calymna)