Appressed-climbing hemiepiphyte; internodes 5-8 cm long, 1 cm diam. at lower nodes, 2-2.5 cm diam. near apex, drying yellow-brown, glossy, longitudinally folded, to 6 mm diam.; cataphylls 15-1 cm long, seemingly unribbed, persisting semi-intact at upper nodes on large stems, drying dark brown, soon weathering to slender, reddish brown fibers, these also mostly deciduous. LEAVES with petioles (9)15-24(36) cm long, typically shorter than the blades, thicker than broad am obtusely sulcate adaxially, 0.5-1 mm diam.; blades narrowly oblong-ovate t weakly oblanceolate-elliptic, 54-75 en long, 12-27 cm wide, broadest at or slightly above the middle, 2.7-4 times longer than wide, 1.1-2.6 times longer than petioles, abruptly acuminate at apex, narrowly acute to truncate to subcordate (rarely cordate) at base; upper surface drying grayisl to grayish brown, with inconspicuous scattering of short, whitish, raphide cellular inclusions; lower surface drying dark yellowish brown, with inconspicuous areolate pattern of depressions; both surfaces drying matte, with a thickened, more or less hyaline, yellowish brown, submarginal band 1.5-2 mm wide, this thicker and more elevated on the lower surface; margins thin, revolute; sinus (when present, arcuate, to 7 cm deep; major veins drying blackened on lower surface; midrib flat on upper surface, thicker than broad on lower surface, drying acute; primary lateral veins 7-9 pairs, arising at a very acute angle then spreading at 30-45° angle to the margin; interprimary veins usually 1 between each pair of primary lateral veins and only slightly less prominent; basal veins 2-4(5) per side, free to base or nearly so, the uppermost arising at 10-20° angle, the lowermost spreading to as much as 90° angle or reflexed. INFLORESCENCES apparently 1 per axil; peduncles mostly 2-6 cm long, rarely to 23 cm long in fruit, drying 4-10 mm diam.; spathe green, sometimes white at anthesis, (10)12-14 cm long, to 2.5 cm diam. on tube; spadix 11.5-13.5 cm long; pistillate portion 3.5-4 cm long, drying 10-13 cm diam.; male portion 9.7 cm long; sterile male portion 6 mm long, 8-13 mm diam.; fertile male portion drying 7-12 mm diam., the constricted portion 6.5-10 mm diam.; ovaries (7)9-10(12)-locular; ovules ca. 5-6 per locale. INFRUCTESCENCE apparently 7 cm long, 3.5 cm diam.; berries bright orange lo reel, the persistent styles 1.2-1.6 mm diam., annular, with the margins paler and with distinct stylar depressions, conspicuously depressed and darker medially; seeds diying dark brown, 1 mm long, 0.4 mm diam.
Philodendron aureimarginatum is most similar to P. wittianum Engl. a species with similar blade shape. That species differs in having shorter internodes, cataphylls that usually persist on the stem and blades that lack hyaline margins.
Occurring in areas of white sand soil, at less than 150 m elevation, in an area of Tropical moist forest (bh-T).
Only from Ecuador and Peru, in the drainage of the Rio Napo. Most of the collections are from the Iquitos area, occurring in areas of white sand soil.