Kingdom Protoctista Hogg, 1860 Phylum Bacillariophyta Engl. & Gilg (1919) - diatoms see [unranked] Diatomea Kütz. (1844) 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) 1 Genus Thalassionema (Grunow ex H. Perag. & Perag.) Perag. (1921)