Plastid and nuclear DNA sequence analyses show that the sub-Saharan African genus Lapeirousia Pourr. is paraphyletic as presently circumscribed. Species of Lapeirousia are retrieved as a clade in which are nested the tropical African genera Cyanixia Goldblatt & J.C.Manning and Savannosiphon Goldblatt & Marais as sister to Lapeirousia sect. Paniculatae Goldblatt plus the taxonomically isolated L. neglecta Goldblatt.
To preserve taxonomic monophyly, Lapeirousia is dismembered, recognising the new genera Codonorhiza Goldblatt & J.C.Manning for L. sect. Fastigiatae Goldblatt (7 spp.) and Schizorhiza Goldblatt & J.C.Manning (1 sp.) for L. neglecta, both from the Cape Floristic Region, as well as Psilosiphon Welw. ex Goldblatt & J.C.Manning (15 spp.) for L. sect. Paniculatae, all from tropical and eastern southern Africa. This leaves Lapeirousia (27 species) centred in western southern Africa, but also represented in south tropical Africa. The infrageneric taxonomy of Lapeirousia is revised in light of the molecular phylogeny, recognising sect. Chasmatocallis (R.C.Foster) Goldblatt & J.C.Manning, sect. Lapeirousia and sect. Sophronia (Licht. ex Roem. & Schult.) Goldblatt & J.C.Manning. Dichotomous keys to the four genera in southern Africa and full revisions of all four genera are provided.
Six new species, two of Codonorhiza, three of Lapeirousia and one Psilosiphon are recognised; two subspecies are raised to species rank, and L. angustifolia Schltr., currently included in L. pyramidalis (Lam.) Goldblatt, is also recognised at species rank. Four new subspecies are described.