The Actinopod sarcodines, of protozoan superclass Actinopoda (a major category of protozoans), share many features with the Rhizopod sarcodines. Primarily marine, they have various types of pseudopodia for locomotion and feeding, tubular mitochondrial cristae, and a structured, elaborate cytoskeleton. Many actinopods incorporate mineral material, such as calcium, into their skeletons. All actinopods are axopods, radially stiffened, and all have a central rod made of microtubules. Most species are marked by complex central capsules made of chitinous material and containing the nucleus, that divide the cytoplasm in half.

Many groups of actinopods are planktonic and free living, and they constitute an important part of the zooplankton community, and thus the food web, in some areas of the ocean. They divide by binary fission, or, for some species, budding or multiple fission. Over half of actinopod species are extinct, of the 12,000 known. One large class, the radiolarians, are marked by complex tests and near-perfect radial symmetry. Pseudopodia extend through perforations in the test. During binary fission in these species, the test usually splits in half, and each daughter cell regenerates half; sometimes, however, one daughter cell gets the whole parent shell and the other grows a new one.

Phyla of the Actinopod sarcodines

• Phylum Actinophyridea
• Phylum Centrohelidea
• Phylum Gymnosphaeridae
• Phylum Desmothoracidia
• Phylum Taxopoda
• Phylum Acantharia
• Phylum Polycystina
• Phylum Phaeodaria