Gyrista

Gyrista is a phylum of heterokont protists containing three diverse groups: the mostly photosynthetic Ochrophyta, the parasitic Pseudofungi, and the recently described group of nanoflagellates known as Bigyromonada. Members of this phylum are characterized by the presence of a helix or a double helix/ring system in the ciliary transition region.

Taxonomic history
Gyrista was first described in 1998 by protistologist Thomas Cavalier-Smith in his work A revised six-kingdom system of life, originally as a superphylum containing two phyla: Ochrophyta, the heterokont algae; and Bigyra, which then contained the pseudofungi and bigyromonads together with the opalines. Later, the name Bigyra was modified to contain opalines, bicosoecids and labyrinthulomycetes, while the Ochrophyta, Pseudofungi and Bigyromonada remained as groups within Gyrista.

Molecular phylogenetics
Gyrista was seen in 2017 as the sister group to phylum Bigyra, which contains the Sagenista and Opalozoa. Together, Gyrista and Bigyra form the superphylum Stramenopiles or Heterokonta.

A phylogenetic analysis in 2022 recovered a monophyletic Bigyromonada sister to Pseudofungi. The "Bigyra" is paraphyletic:

Classification
The 2018 revised taxonomy of Gyrista is the following, with the inclusion of new ochrophyte classes described in 2020 and 2021:
 * Subphylum Bigyromonada
 * Class Developea [=Bigyromonadea ]
 * Class Pirsonea
 * Subphylum Pseudofungi [=Heterokontimycotina ]
 * Class Hyphochytrea [=Hyphochytriomycota ]
 * Class Oomycetes [=Oomycota ; Peronosporomycetes ]
 * Subphylum Ochrophytina [=Heterokontophyta ; Stramenochromes ]
 * Infraphylum Chrysista
 * Superclass Limnistia
 * Class Eustigmatophyceae Hibberd & Leedale (1971)
 * Class Chrysomonadea [=Chrysophyceae ]
 * Class Picophagea [=Synchromophyceae ]
 * Superclass Raphidoistia
 * Class Raphidomonadea
 * Subclass Raphidophycidae
 * Subclass Raphopoda
 * Superclass Fucistia
 * Class Aurophyceae
 * Subclass Aurearenophycidae
 * Subclass Phaeothamniophycidae
 * Class Chrysomerophyceae
 * Class Chrysoparadoxophyceae
 * Class Phaeosacciophyceae
 * Class Schizocladiophyceae
 * Class Phaeophyceae [=Fucophyceae Warming 1884; Melanophyceae ]
 * Subclass Discosporangiophycidae
 * Subclass Ishigeophycidae
 * Subclass Dictyotophycidae
 * Subclass Fucophycidae
 * Class Xanthophyceae [=Tribophyceae ; Heterokontae ]
 * Infraphylum Diatomista
 * Superclass Hypogyrista
 * Class Dictyochophyceae [=Dictyochia ; Alophycidae ]
 * Subclass Pedinellia [=Actinochrysophyceae ; Axodines]
 * Subclass Pelagophycidae
 * ?Subclass Sulcophycidae – ?Sulcochrysis
 * Class Pinguiophyceae
 * Superclass Khakista
 * Class Bolidophyceae
 * Class Diatomeae [=Bacillariophyceae]
 * Subclass Corethrophycidae
 * Subclass Rhizosoleniophycidae
 * Subclass Eucentricophycidae
 * Subclass Bacillariophycidae [=Pennatia ; =Pennatophycidae]
 * Ochrophytina incertae sedis
 * Class Olisthodiscophyceae