Tree, to 20 m tall; leaflet midribs above and axes and calyces of inflorescences puberulent, otherwise glabrous. Rachis and petiole winged, sometimes narrowly so; leaflets in 2 pairs, +/- elliptic, asymmetrical in lower half, acuminate, +/- acute at base, the terminal pair 4.5-12 cm long, 2-4.5 cm wide. Spikes axillary, in groups of 1-4; peduncles usually less than 1 cm long; rachis 4-11 cm long; bracts linear, ca 2 mm long; flowers usually sessile; calyx ca 1 mm long, shallowly lobed; corolla 2-4 mm long, the lobes acute, ca 1 mm long; stamens and style to ca 10 mm long. Legumes flat, the seminiferous areas bulged, 8-14 cm long, 1-2 cm wide. Croat 8185. Similar to I. fagifolia and I. pezizifera, but separated by always having four leaflets and a winged rachis. Costa Rica to Bolivia and Brazil. In Panama, known from tropical moist forest in the Canal Zone, Bocas del Toro, Colón, Chiriqui, and Darien and from premontane wet forest in Coclé. (El Valle).