A molecular phylogeny shows that the small Malagasy endemic genus Achyrocalyx is part of a monophyletic clade with African and Malagasy Stenandriopsis taxa (Mc Dade et al., 2005). Futhermore, Achyrocalyx was recognized by Benoist (1930, 1967) as distinct from Stenandriopsis on the basis of having a bilabiate corolla versus one with the five lobes nearly equal. As many African Stenandriopsis have corollas that are as zygomorphic as those of Achyrocalyx, this would not seem to be a valid distinction between the two genera (Mc Dade et al., 2005: 852). Therefore Achyrocalyx may probably be better placed as a synonym of Stenandriopsis. Benoist annotated Dequaire 27311 (P) with the unpublished name A. cuspidatus, however we believe this specimen can be comfortably included within A. decaryi.