External to the capsule there is a large, often darkly pigmented, mass of granular cytoplasm called "phaeodium" which contains undigested or partially digested food or debris.

Others have ornate spicules scattered through the external cytoplasm in a variety of forms, including geodesic frameworks, spheres or polyhedra.

Some species of the family Challengeriidae resemble marine dinoflagellates, but can be correctly distinguished by the presence of a phaeodium and absence of grooves.

[7] The continuous, massive strand of cytoplasm in the astropyle of Phaeodarea provides a pathway to carry digested prey matter into the endoplasm, similarly to some testate amoebae and foraminifera.

[1] As a protist group often broken by normal sampling methods and not very abundant in comparison with other organisms in the euphotic zone, Phaeodaria have attracted little attention from plankton researchers.

The majority of taxonomic and ecological information regarding Phaeodaria, studied by German scientists, ended after World War I, and it has been little updated until today.

Because of the presence of an organic central capsule and "ray-like pseudopodia", Phaeodaria were historically regarded as Radiolaria, along with Polycystinea and Acantharea.

[7] The marine Radiolaria were, along with the freshwater Heliozoa, assigned to the phylum Actinopoda due to their elaborate siliceous skeletons surrounding the central capsule with pores from which axopodia emerge.