Terrestrial, hemiepiphytic or epilithic shrub. Stem robust, woody, internodes 0.3-0.8 x 8-20 cm, covered by robust (thorn-like) and sparse intravaginal squamules, 8-12 x 3-6 mm, Petioles 70-80 x 2-2.3 cm, canaliculate adaxially,. Leaf blade bipinnatilobed 60- 72 x 50- 56 cm, ovate-sagittate to ovate- cordate in outline, anterior division 40-48 x 50-56 cm, lobes 6-7 per side, each one also pinnatilobed, secondary nerves arising in angle of 60-70°, sinuses between lobes 2-4 cm from midrib, apex acuminate, posterior divisions 16-18 x 50- 56 cm, acroscopic lobes 3-4, basiscopic lobes 2- 3, basal rib denuded for 3.5-4 cm. Inflorescence usually solitary. Peduncle 15-17 x 1-1.5 cm. Spathe 16-18 X 4-11 cm, green outside, white inside. Spadix 15 x 3 cm, fertile male portion 4.5-5 x 1.2-1.5 cm, sterile male portion 6-7 x 2-2.5 cm, female portion 3.6-4 x 2.5-3 cm. Male flowers prismatic, 2-3 x 0.5-0.6 mm, staminodes clavate, 3-5 x 0.8-1 mm, female flowers 4-5 x 2.3 mm. Berries immature 3-4 x 3- 5 mm, ripe fruits not seen.
Stem erect, arborescent, covered with the scars of fallen leaves, with robust axillary prickles. LEAVES: Petioles flattened on the upper side, 62 cm long, 2.5 cm thick; blade triangular-sagittate in outline, bipinnatipartite, primary lateral divisions linear-lanceolate, acute, terminal division 3-furcate at the front, 2-furcate at the back; primary lateral veins distinctly prominent on both sides ('utrique'). INFLORESCENCE: Peduncle 9 cm long. Spathe thick, tube green 11-15 cm long; blade externally green, internally white, ovate cucullate, cuspidate, 8-9 cm long, barely distinct. Spadix: female zone 2.7-4 cm long, dorsally adnate to the spathe almost up to halfway; sterile male zone ('6-5-10') cm long, fertile zone 8.5-10 cm long. Pistils truncate from above, 8-10 locular, ovules 6-9 per locule, bi-tri-seriate; stigma lobes not derived from the margin; Staminodes clavate, 6 mm long.
Philodendron mello-barretoanum ranges from the Brazilian State of Tocantins to Bolivia, occurring at the transition between savannoid formations in Central South America and the Amazon. It is not so common in limestone outcrops as P. lundii but it was recently found growing abundantly in a limestone cliff in Tocantins State.