subsect. Eucardium (Engl.) Mayo,
Bot. J. Linn. Soc.100: 168. 1989.
TYPE: P. wallisii Regel ex Engl. [monotypic]
This is a dubious section, based only on P. wallisii, a poorly known species. The description characterizes the subsection as having scarcely succulent petioles which are flattened to sulcate abaxially, cordiform blades and 5-6 locular ovaries with a few sub-basal ovules per locule. Unfortunately P. wallisii is a poorly known taxon for which, so far as is known, no extant material exists.
Following his treatment of Eucardium, Krause discusses several poorly known species, all of which lacked inflorescences and for which no proper sectional placement was possible. Among these were P. andreanum which is almost certainly related to P. gigas, a member of P. ser. Velveta. Listed among these dubious species are P. latilobum Schott and P. obtusilobum Miq. The former is a synonym of P. panduriforme, possibly a member of P. subsect. Bulaoanum, which it most resembles. Philodendron obtusilobum is a poorly known species of unknown origin, known only from a single leaf. Its affinities remain unknown but it appears similar to P. lindenii Schott or P. rubens Schott.
Also described among this group of unassigned species were P. gloriosum André and P. mamei André. These two species along with P. sodiroi hort. would appear to be closely related and probably constitute a new section. Philodendron pastazanum K. Krause has similar features and probably belongs here also. Another species known from the Amazonian lowlands of Peru and believed to be new is also in this group. All the species in this putative new section are terrestrial plants with a unique growth form for Philodendron. All have a short, repent, creeping stem with erect leaves clustered near the apex. The internodes are usually much broader than long and usually have persistent cataphylls sometimes persisting somewhat intact. The petioles are frequently winged or undulate-winged along adaxial margins (but not P. gloriosum) and blades are typically quite attractive, sometimes mottled with paler green, sometimes (as in P. gloriosum) sometimes somewhat velvety. The group is restricted to South America chiefly in the upper Amazon region. Studies of the ovules are necessary to confirm these speculation and investigations will be carried out as material becomes available.