Clarke originally published the genus in 1895, but as a nomen nudum. It was only validated in 1898. Over the years, circumscription of the genus have varied widely, and several authors have included the genus in Tetraria, but recent work (Bruhl, 1995; Bruhl and Verboom pers. com.) suggests that Costularia in a narrow sense (based on the African and Malagasy spp) probably represents a coherent genus.