[ref. ID; 3960 (Lloyd A. Davidson, 1982)]
Most taxonomic reviews of the helioflagellates have ignored the structural dichotomy between the centrohelidan and the actinophryid types. Tregouboff (1953), for example, in his classification of the heliozoa in Grasse's Traite de Zoologie, includes both types in a single family under the order Proteomyxida and mistakenly describes both Ciliophrys and Actinomonas as containing a central body (corpuscle) rather than a central nucleus. Similarly, Jepps (1956) failed to differentiate in her text between Dimorpha, with its central granule or centroplast, and Actinomonas, with its central nucleus, although she does do so in her figure legend. Hall (1953) lumps all the helioflagellate genera (Acinetactis, Actinomonas, Ciliophrys, Dimorpha, Dimorphella, and Tetradimorpha) in the order Heliofagellida, class Actinopodea, subphylum Sarcodina. Kudo (1966), for some obscure reason, separated Ciliophrys from the other genera, including Actinomonas, and placed it as a separate family within the order Heliozoa and, in his generic diagnosis of Ciliophrys, failed to even mention the central nucleus. He placed the rest of the helioflagellate genera, including Actinomonas with its central nucleus, within the family Mastigamoebidae, order Rhizomastigida, class Sarcodina. In the classification of Honigberg et al. (1964), all the helioflagellates were included in the order Rhizomastigida, class Zoomastigophorea. Only in the most recent classification of Levine et al (1980, see: ref. ID; 923) are the two groups separated correctly.
Suborder Ciliophryina
Ciliophryina contains two genera. Both genera have axopodial axonemes that originate from the outer nuclear membrane of a central nucleus and have tractellar flagella.
Genus Actinomonas, Ciliophrys
Suborder Dimorphina
Dimorphina contains two genera. These genera contain a centroplast like that found in the centrohelidan heliozoa from which the axonemal microtubules originate. The flagellar, mitochondrial, and extrusome morphology of the Dimorphina is not yet known.
Genus Dimorpha and Tetradimorpha