Systematics
This species is very distinct and its nearest relatives are Epiphyllum laui and Epiphyllum anguliger. The flowers of Epiphyllum grandilobum are similar but the stem morphology is very different. Epiphyllum macropterum probably belongs here, but due to lack of type material its identity will never be known, thus that name must be rejected.
Read more about this topic: Epiphyllum Crenatum