Costus callosus sp. nov. is most similar to C. curvibracteatus, differing by the inflorescence mostly produced terminally on a leafless shoot, with soon withering sheaths and bracts with a very long callus.
Herb 0.5–3 m tall. Leaves sheaths 15–30 mm diam; ligule obliquely truncate, 10–30 mm long, distally black to dark purple, with a minute, salient rim; petiole 5–20 mm long; sheaths, ligule and petiole glabrous, sparsely puberulous, or densely villose; lamina narrowly elliptic, 25–50 × 7–16 cm, adaxially sparsely to rather densely villose to puberulous, abaxially rather densely villose, base acute, apex acuminate (acumen 5–15 mm long). Inflorescence ovoid to subglobose, 6–23 × 6–12 cm, terminating a leafless shoot 20–90 cm long, rarely terminating a leafy shoot (Knapp & Vodicka 5524), sheaths withering and completely or partly falling off with age, obliquely truncate, 4–10 cm long, glabrous, sparsely puberulous to densely villose; bracts, bracteole, calyx, ovary, and capsule glabrous to rather densely puberulous. Flowers abaxially oriented; bracts orange-red, red, or yellow, coriaceous, ovate-triangular, 4–7 × 2.5–4 cm, apex acute to obtuse, more or less curved outwards to patent in living plants, callus 8–25 mm long, margins wooly in living material; bracteole boat-shaped, 20–30 mm long; calyx red, 10–18 mm long, lobes deltate, 2–8 mm long; corolla orange to yellow, ca. 50 mm long, glabrous, lobes elliptic, ca. 30 mm long; labellum yellow, lateral lobes rolled inwards and forming a tube ca. 10 mm diam, elliptic when spread out, ca. 35 × 25 mm, 3-lobulate, lobules red, 5–6 mm long; stamen yellow, 35–40 × 12–15 mm, slightly exceeding the labellum, apex orange-red, acute, anther9–10 mm long. Capsule ellipsoid to obovoid, 8–15 mm long.Distribution. Costa Rica, Panama, Colombia (Antioquia, Chocó) (Fig. 21F).Habitat and ecology. In forests, at elevations of 0–1300 m. Flowering year-round