Tree, to 10 (20) m tall; branchlets densely ferruginous-velutinous. Leaves densely rufous to golden-tomentose on axis and veins, sparsely so on leaf surface; rachis widely winged; petioles terete; leaflets in 3 or 4 pairs, ovate to broadly elliptic, acute to acuminate, obtuse to rounded and asymmetrical at base, the terminal pair 13-21 cm long, 6-12 cm wide. Spikes axillary, usually solitary or paired, the axis densely brownish-tomentose; bracts to ca 8 mm long; flowers sessile; calyx 15-21 mm long, glabrous except on tips of teeth, conspicuously longitudinally striate, the lobes to ca 2 mm long, blunt, bearing conspicuous tuft of trichomes at apex; corolla 35-55 mm long, white-sericeous, the lobes to ca 6 mm long; stamens and style to ca 80 mm long. Legumes flat, densely ferruginous-hirsute, 25-45 cm long, 4-6 cm wide, often twisted, the margins raised, rounded. Croat 6858, 12959. Similar to I. goldmanii, but having a long slender corolla, fruit of a lighter reddish-brown color, and no gland near the base of midrib on upper leaflet surface. Known only from Panama, from tropical moist forest in the Canal Zone, San Blas, Panama, and Darien.