QPX was originally considered a chytrid, but has now been provisionally assigned to the phylum Labyrinthulomycota in either the Thraustochytriidae or the Labyrinthulidae family, based on the organism having a " uninucleate biflagellate zoospore stage, a loose multilaminar cell wall, and particularly an intracellular sagenogen-like structure ".
12.
The current practice is the ( questionable ) synonymous use, based on morphological similarity, of the generic names " Monas " ( mostly used in the east-Asian literature ) and " Spumella " ( synonymously used in the European and American literature ) as unpigmented biflagellates in Chrysophyceae.
