Division Bacillariophyta Engl. & Gilg (1919) see Phylum Bacillariophyta Engl. & Gilg (1919)
   Class Fragilariophyceae Round (1990) - araphid, pennate diatoms see Class Bacillariophyceae Haeckel (1878)
     Subclass Fragilariophycidae Round (1990) - core araphid diatoms
       Order Thalassionematales Round (1990)
         Family Thalassionemataceae Round (1990)
           Genus Trichotoxon F. Reid & Round (1988)