Kingdom Protoctista Hogg, 1860
   Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844)
     Class Coscinodiscophyceae Round & R.M. Crawford (1990) - radial centrics
       Subclass Coscinodiscophycidae Round & R.M. Crawford (1990)
         1 Order Chrysanthemodiscales Round (1990)
         2 Order Melosirales R.M. Crawford (1990)
         3 Order Paraliales R.M. Crawford (1990)
         4 Order Aulacosirales (R.M. Crawford, 1990) see Order Aulacoseirales R.M. Crawford (1990)
         5 Order Coscinodiscales Round & R.M. Crawford (1990)
         6 Order Ethmodiscales Round (1990)
         7 Order Stictocyclales Round (1990)
         8 Order Asterolamprales Round & R.M. Crawford (1990)
         9 Order Arachnoidiscales Round (1990)