Large tree up to 18–25 m. high; crown rounded, with pendulous branchlets; bark brown to almost black, deeply longitudinally fissured. Young branchlets glabrous to pubescent, grey-brown. Stipules spinescent, straight or nearly so, some short, to about 7 mm. long, others long, whitish, to about 9 cm. long, sometimes modified to inflated fusiform “ant-galls.” Leaves: rhachis 1–6 cm. long; pinnae 5–13 pairs, some leaves normally with 8 or more pairs; leaflets (7–)13–25 pairs per pinna, 1.25–4 mm. long, 0.5–1.25 mm. wide, glabrous or ciliate. Flowers greenish-white to white or very pale yellow, in heads on peduncles 2–5 cm. long, whose involucel is about ⅓-½-way above base. Pods straight, narrowly oblong, dehiscent, 3–12 cm. long, 1.2–1.8 cm. wide, shortly attenuate at base, acuminate or rounded at apex, brown or purplish-brown, finely and mostly obliquely veined, glabrous or ± pubescent near base. Seeds oblique in the pod, olive-brown, smooth, subcircular, compressed, 6–7 mm. diam.; areole 3–5 mm. long, 3.5–4 mm. wide.
