Kingdom Protoctista Hogg, 1860
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
     Class Bacillariophyceae Haeckel (1878) - pennates
       1 Subclass Eunotiophycidae D.G.Mann (1990) see Subclass Bacillariophycidae D.G.Mann (1990)
       2 Subclass Bacillariophycidae D.G.Mann (1990) - raphid diatoms