Unarmed shrub or tree up to 15 m high with a conical or rounded crown; bark grey-brown to blackish, smooth or rough on very old trunks; young branchlets usually densely short-pubescent, rarely subglabrous, ± grey-pruinose, indumentum grey or sometimes yellowish at first and then grey. Leaves bipinnate, often glaucous; petiole 0,5-2 cm long, eglandular; rhachis 2,5-10 cm long, with a raised gland on its upper surface at the junction of each pair of pinnae, but without other glands in between the pinnae pairs as in A. meamsii; pinnae (5)10-26 pairs; leaflets in 17-50 pairs, 2-5,5 x 0,4-0,7 mm, linear-oblong, sparingly to ± densely pubes­cent or glabrous beneath, margins with or without cilia. Inflorescences capitate, panicled or racemose. Flowers bright yellow; peduncles densely pubescent, up to 6 mm long. Calyx and corolla glabrous except for apices of the lobes. Pods 3-8 x 0,7-1,3 cm, not or only slightly moniliform, dehiscing longitudinally along one margin only, straight or slightly curved. Seeds brown to blackish-brown, 5-6 x 3-3,5 mm, elliptic, compressed, smooth; caruncle conspicuous; areole 3,5-4 x 0,75-1,5mm.