This is a seemingly quite natural group characterized by having scaly petioles. As defined by Schott (1856) it was represented only by the type species, P. verrucosum. Krause (1913) included six species, aside from the aforementioned they are: P. nanegalense Engl., P. pilatonense Engl., and P. gualeanum Engl. (all of which, I believe, represent a single species), as well as P. serpens Hook. f. All but P. verrucosum were known only from South America. There are several other undescribed species now known from South America.
Philodendron subsect. Achyropodium is largely restricted to the northern Andes and lower Central America (Costa Rica and Panama) but has one species, P. verrucosum, that ranges as far south as Peru. The subsection is represented in Central America by P. glanduliferum var. glanduliferum, P. hammelii, P. malesevichiae, P. squamicaule, P. squamipetiolatum, and P. verrucosum.