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.
