What is "radiolaria"

Radiolaria \Ra`di*o*la"ri*a\ (r[=a]`d[i^]*[-o]*l[=a]"r[i^]*[.a]), n. pl. [NL. See Radioli.] (Zo["o]l.) Order of rhizopods, usually having a siliceous skeleton, or shell, and sometimes radiating spicules. The pseudopodia project from the body like rays. It includes the polycystines. See Polycystina.

n. The members of the taxonomic subclass Radiolaria; radiolarians.

The Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. They are found as zooplankton throughout the ocean, and their skeletal remains make up a large part of the cover of the ocean floor as siliceous ooze. Due to their rapid turn-over of species, they represent an important diagnostic fossil found from the Cambrian onwards. Some common radiolarian fossils include Actinomma, Heliosphaera and Hexadoridium.