There are six undescribed species of Cyphostemma in Madagascar. Descoings had previously segregated two undescribed species from Ankara and Marojejy. Four additional undescribed species have been identified while assessing this genus for the Catalogue of Plants of Madagascar. If additional material becomes available that can complement the unidentified specimens, then there may be a further two undescribed species.
Four taxa could not be evaluated because the type material and specimens could not be located in the P herbarium; these are: C. leandrii, C. tsaratananensis, C. microdiptera, C. macrocarpa var. minutiflora. The type specimen of C. microdiptera is not yet known, but may be a Kitching specimen at Kew.