A group of one-celled marine animals with a siliceous skeleton that occupies shallow portions of the water column. Radiolarians have a range from Cambrian to present.

Any actinopod animal belonging to the subclass radiolaria, characterized by a silica skeleton and dwelling in a marine pelagic environment.

A creature which lives inside a shell which is covered in spikes and spines

one of a group of usually planktonic, amoeba-like animals with a shell.

protozoa with amoeba-like bodies and radiating filamentous pseudopods

single-celled heterotrophic organisms with elaborate skeletons made of silica. These silica skeletons are so durable that radiolarian fossils are used to date deep-sea sediments.

Radiolarians (also radiolaria) are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. They are found as plankton throughout the ocean, and because of their rapid turn-over of species, their tests are important diagnostic fossils found from the Cambrian onwards. Some common radiolarian fossils include Actinomma, Heliosphaera and Hexadoridium.