Cercozoa
The Cercozoa are a group of single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, being defined by molecular phylogenies of rRNA and actin or polyubiquitin. They are the natural predators of many species of microbacteria and Archea. Characteristics. The group includes most amoeboids and flagellates that feed by means of filose pseudopods. These may be restricted to part of the cell surface, but there is never a true cytostome or mouth as found in many other protozoa. They show a variety of forms and have proven difficult to define in terms of structural characteristics, although  their unity is strongly supported by genetic studies. Cercozoa are closely related to Foraminifera and Radiolaria, amoeboids that usually have complex shells, and together with them form a supergroup called the Rhizaria. Types. They are sometimes grouped by whether they are "filose" or "reticulose". Filose (subphylum Filosa). The best-known Cercozoa are the euglyphids, filose amoebae with shells of siliceous scales or plates, which are commonly found in soils, nutrient-rich waters, and on aquatic plants. Some other filose amoebae produce organic shells, including the tectofilosids and "Gromia". They were formerly classified with the euglyphids as the Testaceafilosia. This group  is not monophyletic, but nearly all studied members fall in or near the Cercozoa, related to similarly shelled flagellates. Other notable filose cercozoans include the cercomonads, which are common soil flagellates. Reticulose (subphylum Endomyxa). Another important group placed here are the chlorarachniophytes, strange amoebae that form a reticulating net. They are set apart by the presence of chloroplasts, which apparently developed from an ingested green alga. They are bound by four membranes and still possess a vestigial nucleus, called a nucleomorph. As such, they have been of great interest to researchers studying the endosymbiotic origins of organelles. Chlorarachniophytes are sometimes  considered Filosa, rather than Endomyxa, while groups such as "Gromia" are considered Endomyxa. Filosa is apparently a monophyletic group, but Endomyxa is paraphyletic. Ungrouped. In addition, three groups that are traditionally considered heliozoans belong here: the Heliomonadida, Desmothoracida, and Gymnosphaerida, which were recently grouped into the new class of Granofilosea. Finally, cercozoans include the Phaeodarea, marine protozoa that were previously considered radiolarians. Classification. The exact composition and classification of the Cercozoa are still being worked out. A general scheme is: In addition two groups of parasites, the Phytomyxea and Ascetosporea, and the shelled amoeba "Gromia" may be basal Cercozoa, although  some trees place them closer to the Foraminifera. The spongomonads have been included here, but more recently have been considered Amoebozoa. Some other small groups of protozoans are considered Cercozoa but are of uncertain placement, and it is likely many obscure genera will turn out to be cercozoans with further study. Phylogeny. Phylogeny based on Bass et al. 2009, Howe etal. 2011 and Silar 2016. In 2019, Cercozoa were recognized as sister to Retaria in Rhizaria. Taxonomy. Phylum Cercozoa Recently an orphan protist Quadricilia rotundata finally finds fts phylogenetic home in Cercozoa.