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)
         Order Arachnoidiscales Round (1990)
           Family Arachnoidiscaceae Round (1990)
             Genus Arachnoidiscus H. Deane pat. ex Shadbolt (1852)