Opalozoa is a subphylum of heterotrophic protists of the phylum Bigyra, and is the sister group to Sagenista.

[2][1] Opalozoans are non-photosynthetic heterokonts that are ancestrally phagotrophic but many times have evolved to be osmotrophic saprotrophs in the gut of vertebrate animals.

[3] In 1993 the name “Opalozoa” referred to a group of protists that was very different from what it is now.

It was a phylum composed of many unrelated zooflagellates, grouped together because of the common presence of tubular mitochondrial cristae and the lack of cortical alveoli or rigid tubular ciliary hairs (retronemes).

[1] Opalinea Blastocystea Opalomonadea Nanomonadea Placididea Pseudodendromonadida Bicoecida Anoecida Borokida Rictida