Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         [crown] Clade Biota Wagner 2004 [Wiemann, de Queiroz, Rowe, Planavsky, Anderson, Gogarten, Turner & Gauthier 2020]
           Clade neomura Cavalier-Smith, 1987
             Domain Eukaryota Chatton, 1925 - eukaryotes
               Clade discaria Cavalier-Smith, 2021
                 Clade natates Cavalier-Smith, 2021
                   Clade photaria Cavalier-Smith, 2021
                     Clade eucorta Cavalier-Smith, 2021
                       Superkingdom Corticata Lankester, 1878 - corticates
                         Kingdom Chromista Caval.-Sm. (1981) - chromists
                           Subkingdom Harosa Cavalier-Smith, 2010
                             [crown] Clade Sar Adl et al. 2012 [Simpson & Dunthorn 2020]
                               Infrakingdom Halvaria Cavalier-Smith, 2010
                                 Superphylum Heterokonta Caval.-Sm. (1986)
                                   Phylum Ochrophyta Caval.-Sm. (1995)
                                     Subphylum Khakista Caval.-Sm. (2000)
                                       Diatomea Kütz. (1844)
                                         Class Mediophyceae Medlin & Kaczmarska (2004) [paraphyletic] - bipolar centrics
                                           Order Biddulphiales Willi Krieg. (1954) [monotypic]
                                             Family Biddulphiaceaeᵀ Kütz. (1844)
                                               1 Genus Biddulphiaᵀ Gray (1821)
                                               2 Genus Biddulphiopsis Stosch & Simonsen (1984)
                                               3 Genus Hydrosera G.C. Wall. (1858)
                                               4 Genus Isthmia C.Agardh (1832)
                                               5 Genus Pseudotriceratium Grunow (1884)
                                               6 Genus Terpsinoe Ehrenb. (1843)
                                               7 Genus Trigonium Cleve (1868)