Trees, mostly 6-10 (15) m tall; trunks usually less than 20 cm dbh, branching infrequently; wood moderately hard. Leaves alternate, crowded at ends of stout branches; petioles very short or to 11 cm long on juveniles; blades elliptic-oblanceolate, abruptly acuminate, narrowly cuneate and more or less decurrent onto petiole, mostly to 1 m or more long and 25 cm wide, glabrous, coarsely toothed. Corymb short, beneath leaves; pedicels stout, to ca 8 cm long, minutely puberulent; flowers mostly to 12 cm diam; hypanthium turbinate, to 2.5 cm wide; calyx obscure; petals 6-12, unequal, +/- spatulate, oblong, to 7 cm long and 3.5 cm wide, white to cream or spotted with lavender, especially on outside; stamens many, ca 4 cm long, fused one-third their length into a yellowish ring; filaments fleshy, arched inward, often tinged with lavender above, constricted just below anther; stigma short-conical. Pyxidia depressed-globose, 7-10 cm broad, to ca 8 cm long, indehiscent, baccate, with a prominent raised ring at apex, green or pale yellow to orange at maturity with irregular brown lenticels and minute longitudinal ribs, often with a foul odor at maturity; seeds few, fleshy, irregularly shaped, to ca 6 cm long. Croat 5095, 8812. The species is easily confused with G. grandibracteata Croat & Mori, which is to be expected on the island. The key for this family gives the distinguishing characteristics. Woodson and Schery in the Flora of Panama (1958a) reported the range of G. superba to be as far south as Ecuador; they were confusing the species with G. angustifolia Benth., which occurs there.