The ochrophytes, subphylum Ochrophytina, is a group of mostly photosynthetic heterokonts. Their plastid is of red algal origin. The classification of the group is still being worked out. Originally, the ochrophytes were regarded as a phylum denominated Ochrophyta. Some authors (e.g., Cavalier-Smith) divided it into two subphyla, Phaeista Cavalier-Smith 1995 (comprising Hypogyristea and Chrysista in some classifications, or Limnista and Marista in others) and Khakista Cavalier-Smith, 2000 (comprising Bolidomonas and diatoms). Others prefer not to use the subphyla, listing only lower taxa (e.g., Reviers, 2002, Guiry & Guiry, 2014). However, it is currently regarded as a subphylum inside of the phylum Gyrista, along with Pseudofungi and Bigyromonada. It contains two infraphyla: Diatomista, containing diatoms and related groups, and Chrysista, containing brown and golden algae and related groups. Phylogeny The cladogram below shows the evolutionary relationships between all ochrophyte classes. It is based on the latest phylogenetic analyses: Classification Below is the present classification of ochrophytes, with the inclusion of three new classes of algae described in 2019, 2020 and 2021. Infraphylum Chrysista Superclass Limnistia Class Eustigmatophyceae 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 ; Melanophyceae ] (“brown algae”) Subclass Discosporangiophycidae Subclass Ishigeophycidae Subclass Dictyotophycidae Subclass Fucophycidae Class Xanthophyceae [=Tribophyceae ; Heterokontae ] (“yellow-green algae”) Infraphylum Diatomista Superclass Hypogyrista Class Dictyochophyceae [=Dictyochia ; Alophycidae ] Subclass Pedinellia [=Actinochrysophyceae ] (“axodines”) Subclass Pelagophycidae [=Pelagophyceae ] ?Subclass Sulcophycidae Class Pinguiophyceae Superclass Khakista Class Bolidophyceae Class Diatomeae [=Bacillariae ; Bacillariophyceae ] Subclass Corethrophycidae Subclass Rhizosoleniophycidae Subclass Eucentricophycidae Subclass Bacillariophycidae [=Pennatia ; =Pennatophycidae] Ochrophytina incertae sedis Class Olisthodiscophyceae Notes References SAR supergroup phyla