Radiolarian definitions

Any of various marine protozoans of the order (or phylum) Radiolaria, having rigid siliceous skeletons and spicules.

Any of several classes of one-celled deep-sea protozoans with long, slender pseudopodia and a spiny, or solid but perforated, skeleton of silica.

Any of various marine protozoans of the group Radiolaria, having rigid skeletons usually made of silica. The skeletons are usually spherically symmetrical and structurally complex, containing elaborate patterns of perforations (through which pseudopods extend) and often spicules. Skeletal remains of radiolarians sink to form ooze on the ocean floor, and prehistoric radiolarian ooze has fossilized to become chert and flint.