Trunk generally subterranean, sometimes to 60 × 25 cm above ground, base swollen; bark dark gray and scaly toward apex of trunk, white-gray and nearly smooth toward base. Leaves 25-40, 1-pinnate, 1-2 m × 25-55 cm; petiole subterete, 30-70 cm, with (0-)8-21 spines along each side, densely rusty brown tomentose when young; leaf blade oblong, flat; leaflets in 60-100 pairs, longitudinally inserted at ca. 90° to rachis, not overlapping, straight or downcurved, 13-18 cm × 5-12 mm, papery to subleathery, densely red-brown tomentose abaxially when maturing, later becoming light green and sparsely tomentose, midvein raised on both surfaces, base attenuate, symmetric, margin strongly revolute, apex acute to acuminate, somewhat soft at maturity. Cataphylls triangular, 3-4 × 1-1.3 cm, brown tomentose, apex soft. Pollen cones ovoid-fusiform, 20-30 × 6-8 cm; microsporophylls broadly cuneate, 1.5-3 × 1.2-1.5 cm, apical (sterile) part subrhombic, thickened, densely pale brown tomentose, margin inconspicuously toothed, apex with upcurved mucro. Megasporophylls more than 30, tightly grouped, 8-14 cm, tawny tomentose; stalk 4.5-7.5 cm; sterile blade rhombic-ovate, 3.5-5.5 × 3-5 cm, margin glabrescent and pectinate, with 17-31 subulate lobes 1-2.5 cm, terminal lobe subulate, 3-4 cm; ovules 2 or 3 on each side of stalk, glabrous. Seeds 2-4, yellowish when fresh, brown when dry, obovoid or subglobose, 2-2.8 × 1.8-2.5 cm, apex mucronate; sclerotesta smooth. Pollination Mar-Apr, seed maturity Aug-Oct.