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 Plagiogrammales Round & R.M. Crawford (1990) see Order Plagiogrammales Gogorev & Stepanova (2015) 1 Family Plagiogrammaceae De Toni (1890)