Small, monoecious tree, 5-8 m tall, often growing as single plants; trunk less than 5 cm diam; internodes obscurely spiny, the spines 1-6 cm long, dull, black, broadened at base. Leaves 2.5-3 m long; petioles usually ca 1 m long, round, canaliculate above, slightly rufous beneath, spiny only at base or rarely throughout its length (especially true of juvenile plants), the spines 1-8.5 cm long; rachis usually unarmed, green above, rufous below; leaflets 25 or more pairs, to 70 cm long, 2-4 cm wide, glabrous, gray-green, dull, the midrib very prominent above, scarcely more prominent than strong lateral veins below, the cross-veins very prominent on both surfaces, the upper surface with occasional setae, the lower surface sometimes with rufescent bands, the margins usually sparsely but prominently setose, especially near apex, the setae 5-10 mm long or more; apex of leaflets oblique, 3-4 cm long in the middle and distal parts of leaf, to 12 cm long on proximal leaflets; distal leaflets regularly arranged, becoming clustered in groups of 3 or 4, the groups 2-6 cm apart, but with gaps to 30 cm on either side, the proximal leaflets of each group inserted at a higher angle and held above the plane of the leaf, the lowermost pair of leaflets at base of blade sometimes inverted with the bottom side up, the apex of leaflet pointing toward apex of blade; juvenile leaves at first entire, becoming pinnate, the outermost pair broad, the leaflets characterized by having extremely long spines on margin and on upper surface. Spathe 25 cm long, densely brown-spiny, usually falling before fruit matures; peduncle short, somewhat flattened, closely curved, densely covered with short, stiff, brown trichomes at least toward apex; fertile part of spadix 15-25 cm long, widely branched, the branches 20-30, to 2 mm thick. Fruits orange, fading on drying, glabrous, +/- round to obovoid, 1-2 cm long, obtuse and beakless at apex but drying with a blunt beak; cupule small and shallow, almost entire, the outer series very reduced; seed 1. Croat 15422.