The Phaeodarea are a group of amoeboid protozoa. They are traditionally considered radiolarians, but in molecular trees do not appear to be close relatives of the other groups, and are instead placed among the Cercozoa. They are distinguished by the structure of their central capsule and by the presence of a phaeodium, an aggregate of waste particles within the cell.

Phaeodarea produce hollow skeletons composed of amorphous silica and organic material, which rarely fossilize. The endoplasm is divided by a cape with three openings, of which one gives rise to feeding pseudopods, and the others let through bundles of microtubules that support the axopods. Unlike other radiolarians, there are no cross-bridges between them. They also lack symbiotic algae, generally living below the photic zone, and do not produce any strontium sulphate.

References

• Sergey I. Nikolaev et al. (2004). The twilight of the Heliozoa and rise of the Rhizaria, an emerging supergroup of amoeboid eukaryotes. Proceedings of the National Academy of Sciences 101: 8066-8071.