As here circumscribed the family Salviniaceae includes the family Azollaceae, in accordance with updated phylogenetic research (Smith & al. 2006).
- Floating leaves 1-2 mm long, abaxially without papillae. Stem glabrous === Azolla
- Floating leaves ca. 10-20 mm long, abaxially with distinct papillae. Stem hairy === Salvinia
Smith A.R., Pryer K.M., Schuettpelz E., Korall P., Schneider H. & Wolf P.G. (2006) A classification for extant ferns. Taxon 55(3): 705-731.