Herb perennial, hemiepiphytic. internodes 0.5–3.0 cm long, cylindrical, glossy green to brownish, drying paler brown; intravaginal squamules absent. Prophyll 10.5–12.0 × 0.7–1.0 cm, navicular, deciduous, 2-keeled, smooth, cream, drying dark brown. Petiole 15.0–32.0 × 0.5 cm, semiterete to terete, glossy green, not striated, drying brown; leaf blade 23–32 × 16–24 cm, broad ovate to ovate, cordate-sagittate, sometimes slightly asymmetric, apex acuminate, acumen 0.5 cm long, curved, margin entire, base cordate, membranaceous, smooth, strongly discolor, glossy green adaxially, paler abaxially, drying chartaceous, striated, brownish, slightly discolor; anterior division 16.5–24.0 cm long, midrib impressed on both faces, drying paler to dark brown, primary lateral veins 5–6 pairs, arising from midrib at 50–60º angle, arcuate to margin, impressed on both faces, drying paler to dark brown on both faces, prominent abaxially, secondary veins conspicuous, parallel to primary veins, numerous, drying evident and prominent on both faces; posterior divisions 6.0–8.0 cm long, cordate, 2–3 primary acroscopic veins, basal denudation 1.5–2.5 cm long. inflorescence 2–3 per floral sympodium; peduncle 15–30 cm long, longer in the external inflorescences, cylindrical, glossy green, striated; spathe 6.5–13.5 cm long, ovate, acuminate, acumen 0.5–1.0 cm long, slightly constricted, externally green towards the apex, dark violet at the base, striated, internally green towards the apex, reddish-green to vinaceous at the base, resin canals internally visible; stipe absent; spadix 6.0–11.5 cm long, thick; fertile male zone 4.5– 7.0 cm long, greenish; intermediate sterile zone 0.3–0.5 cm long, cream; female zone 2.0–3.5 cm long, green; stamens ca. 2.0 mm long, (2–) 4 grouped, prismatic; intermediate staminodes ca. 3.0 mm long, prismatic; gynoecium 3.0–4.0 mm long, ovary barrel-shaped, 7–8-locular, 3–4-ovulated, placentation basal. Berries unknown. Seeds unknown.
Conservation status:—For now, the species must be considered as Data Deficient (DD), as more information is needed regarding the populations and their geographic distribution. However, due to the singularity of RBME, compound of patches of different phytophysiognomies of Atlantic Forest and ecotones, and to the surrounding area highly deforested (Melo 2005), it will not be surprisingly if P. theofiloanum are restrict to there. Satellite images show that the peculiar vegetation of RBME extend northwest close to the limits of Espinhaço Range, but are strongly modified, especially by mining activity, and probably other areas suitable to the occurrence of P. theofiloanum must be almost completely degraded.
As a general field observation, in the mountain ranges of the Southern Brazilian Atlantic Forest, many species of Philodendron founds optimal conditions to grown up to 800-900 m in elevation, especially in those relatively close to the coast. This can be easily observed through the altitudinal gradient in mountain ranges like Serra dos Órgãos (Rio de Janeiro State), Itatiaia (Rio de Janeiro and São Paulo States) or Caparaó (Espírito Santo and Minas Gerais States). In RBME, however, Philodendron species occur beyond this altitudinal range and form dense populations much more distant from the influence of coastal moisture, what can indicate some peculiarity in this Atlantic Forest remnant or perhaps in the species adaptability.
Philodendron theofiloanum is most similar to the Amazonian Philodendron megalophyllum Schott, but the former has cordate-sagittate leaves, ovary 7–8-locular and locules 3–4-ovulated.
Distribution and ecology:—The new species is only known from the populations at RBME, a conservation unit located nears the Jequitinhonha River, in Jequitinhonha municipality, northeastern region of Minas Gerais State (Figure 3). RBME represents remnants of Atlantic Forest surrounded by Cerrado and Caatinga in patches of Seasonal Semideciduous Forest, Seasonal Deciduous Forest, Ombrophilous Dense Forest and high-altitude grassland with sandy soil (“refúgios ecológicos”, sensu IBGE 2012) (Melo 2005) (Figure 4). Philodendron theofiloanum was only found growing as hemiepiphyte in Ombrophilous Dense Forest and riparian forest inside Seasonal Semideciduous Forest, ranging from 950 to 1100 m in elevation.