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 Bacillariophyceae Haeckel (1878) - pennates
                                           Subclass Bacillariophycidaeᵀ D.G.Mann (1990) - raphid diatoms
                                             Order Bacillarialesᵀ Hendey (1937) [monotypic]
                                               Family Bacillariaceaeᵀ Ehrenb. (1831)
                                                 Genus Nitzschia Hassall (1845)
                                                   Nitzschia sigma (Kützing) W.Sm. (1853)
                                                     Nitzschia sigma var. intercedens Grunow (1878)
                                                     Nitzschia sigma var. rigida (Kützing) Grunow (1878)
                                                     Nitzschia sigma var. rigidula Grunow, in Van Heurck (1881)
                                                     Nitzschia sigma var. sigmaᵀ