Cyrtochilum macranthum (Lindl.) Kraenzl., Notizbl. Bot. Gart. Berlin-Dahlem 7: 95. 1917. h Oncidium macranthum Lindl., Gen. Sp. Orchid. Pl.: 205. 1833. TYPE: Peru. Ruiz & Pavón s.n. (holotype, K; isotype, BM).

Rhizome creeping. Pseudobulbs more or less distant or subcaespitose, up to 10 cm long and 4 cm wide, ovoid, somewhat compressed, subtended basally by leafy sheaths. Leaves 1–2, up to 40 cm long and 5 cm wide, oblanceolate, acute. Inflorescence up to 300 cm long, wiry, paniculate, with well-spaced, few-flowered branches. Flowers large, showy, sepals yellow to deep bronze, petals bright yellow with brown suffusion, lip lilac to purple with yellow middle lobe, callus white and purple. Floral bracts 25–30 mm long Pedicel and ovary up to 65 mm long. Dorsal sepal clawed; claw about 5–10 mm long,
narrow, canaliculate, with elliptic-rhombic wings just above the base; blade 27–35 mm
long, 24–30 mm wide, suborbicular, base subcordate, margins somewhat irregularly
undulate, apex rounded. Petals clawed; claw about 3–5 mm long, basally somewhat
winged; blade 38–42 mm long, 34–35 mm wide when spread, somewhat oblique, broadly
elliptic-ovate, obtuse or truncate at the apex, base subcordate, margins somewhat undulate. Lateral sepals clawed; claw 8–15 mm long, narrow, with basal wing on the outer margin; blade up to 35 mm long, 22–26 mm wide, obliquely elliptic-ovate in general outline, basally rounded, subobtuse at the apex, margins very slightly undulate. Lip 18–30 mm long in total, 12–23 mm wide, triangular in outline, base truncate-subcordate, convex in the centre, callus prominent, complicated, in form of elevated keel apically 3-lobed and flanked basally by 3-lobed process; apical part linear-triangular to ligulate-lanceolate, acute. Gynostemium 9–11 mm long, subarcuate, connate basally with the lip, lateral appendages obliquely obtriangular, not reaching the anther base (Figs. 11 and 12). Ecology: Epiphytic or terrestrial, growing in understory of cloud forest.
Distribution: Colombia (Schweinfurth, 1961), Ecuador, Peru. Alt. 2,200–2,500 m.
Notes: Cyrtochilum macranthum is an easily recognisable species by having large, yellow or yellow with brown suffusion flowers, hastate lip with very prominent lip callus in form of elevated keel apically 3-lobed and flanked basally by 3-lobed process. This species can be compared to C. xanthocinctum but has different lip callus with spreading lateral keels