Stomatium Schwantes in Z. Sukkulentenk. 2: 175. 1926 sec. Hartmann (2001b)
  • Agnirictus Schwantes in Monatsschr. Deutsch. Kakteen-Ges. 2: 21. 1930, nom. inval., syn. sec. Hartmann (2001b)
    • Type: not designated



Stomatium currently includes 39 species, but lacks a taxonomic revision. It was shown to be closely related to Neohenricia (2 spp.), Mossia (1 sp.), Chasmatophyllum (8 spp.), Rhinephyllum (11 spp.) and Peersia (3 spp.) by Klak & al. (2013). Both Rhinephyllum and Chasmatophyllum also lack a taxonomic revision. All of these genera occur outside the winter-rainfall region of South Africa. The group shares a similar floral morphology, i.e. yellow or more rarely cream-coloured petaloid staminodes, absence of filamentous staminodes and a concavely shaped ovary wall. Over the past decades species have been shifted between genera since generic boundaries are poorly circumscribed.