Small, monoecious tree, 3-4 (6) m tall, forming open colonies; plants connected by subterranean stems; trunk 3-4 cm diam; internodes weakly spiny, the spines 1-4 cm long. Leaves 2-3.3 m long, irregularly pinnate, spiny all over or only on base of petiole; petioles terete, to 1.4 m long, furfuraceous on lower side only or all over with only the upper surface near base glabrous, the vaginate base to 40 cm long, spiny throughout its length, the spines solid black to stramineous and black-tipped, l-7 cm long (mostly 4 cm); rachis ribbed at base, becoming triangulate distally, sparsely spiny, the spines like those of the longer type on petiole; leaflets ca 23 pairs, 30-75 cm long, 2.5-6 cm broad, thin, glossy, lacking prominent side ribs or cross-veins, usually with narrow furfuraceous bands near margins on lower surface, prominently setose at apex, the apex falcate, oblique, very long-caudate and drooping, the acumen to 6 cm long on upper leaflets, to 14 cm long on lower leaflets; upper leaflets +/- regularly arranged, the lower becoming arranged in groups of 4-12, each group 5-20 cm apart, the leaflets of each group inserted at staggered angles, the lowermost pair of pinnae at base of blade often held almost vertical forming nearly a right angle with rachis. Spathe 20-35 cm long, +/- caudate at apex, often persisting in fruit, densely setose, the trichomes brown to sienna, at first appressed, later +/- erect, the slender, unarmed base nearly as long as broadened part of spathe; spadix with usually 15-20 well-spaced branches, the branches to 25 cm long, 1.5-3.0 mm thick; staminate flowers pedicellate, the pedicel to 1 mm long, slender; sepals 3, very slender, ca 1 mm long; petals 3, accrescent in lower half, acute, ca 4 mm long; pistillate flowers ca 4 mm long, the envelopes striate, the inner ones short and truncate, the outer with 3 acute lobes. Fruits turbinate, 1.5-2.5 cm long, with abrupt, short, slender beak, green to black, sparsely hirtellous, becoming +/- glabrous at maturity; cupule double with bluntly scalloped edges; seed 1. Croat 6772, 8787. Abundant in the forest, usually in small or large stands; juveniles often very abundant. Plants are not commonly seen in flower, apparently not flowering every year; numerous individuals flower, but only a small part of the adult population. Flowers in the middle to late dry season, with fruits maturing in the early rainy season, mostly in August and September.