Kingdom Protoctista Hogg, 1860
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
     Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
       1 Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
       2 Subclass Chaetocerophycidae see Subclass Chaetocerotophycidae Round & R.M. Crawford (1990)
       3 Subclass Rhizosoleniophycidae Round & R.M. Crawford (1990)
       4 Subclass Lithodesmiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
       5 Subclass Biddulphiophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
       6 Subclass Thalassiosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)
       7 Subclass Corethrophycidae Round & R.M. Crawford (1990)
       8 Subclass Cymatosirophycidae Round & R.M. Crawford (1990) see Class Mediophyceae Medlin & Kaczmarska (2004)