Liana or arching shrub, to 9 m tall; younger stems sparsely pubescent, becoming glabrous in age. Leaves quaternate, sometimes opposite or alternate apically, subsessile or borne on petioles to 5 mm long; blades obovate to oblanceolate, shortly and abruptly acuminate, obtuse to acute and decurrent on petiole at base, 8-16 cm long, 3-6 cm wide, glabrous or sparsely pubescent below especially on veins, with a submarginal collecting vein. Flowers few, in subterminal cymes; pedicels 2-7 mm long; bracteoles minute; calyx lobes 5, irregular, +/- oblong-linear, acute, to 14 mm long; corolla yellow, 8-12 cm wide, the tube to 3.5 cm long, the throat broadened and as long as tube, the lobes 2.5-3.5 cm long, +/- rounded, imbricate; stamens situated just above tube; filaments fused to tube, retrorsely barbellate near apex; anthers sharply triangular, free but with their apices held tightly together, the ring of anthers covered above by long, straight trichomes pointing inward from wall of corolla; ovary at first smooth, becoming spiny; style slender, its apex broadly expanded, plungerlike, situated inside the ring of anthers; stigmas 2, short. Capsules +/- ellipsoid to obovoid, spiny, 5-8 cm long excluding spines, green at maturity, the spines 5-20 mm long; seeds numerous, disk-shaped, 2-2.5 cm diam, concentrically winged. Croat 6573. The ovary is surrounded by an active nectary. The broad cylindrical part of the style is also covered with a thick substance, which may attract the pollinator. In the plant's native habitat, the pollinator is unknown, but the organism would need a tongue 3.5-4 cm long to reach the nectar at the base of the constricted tube. Presumably the pollinator's head is thrust into the upper flared part of the corolla. Fruits are occasionally produced in central Panama, so some pollinator must be effective.