Trunk often subterranean, cylindric or flask-shaped, sometimes moniliform, to 50 × 15 cm, base abruptly swollen to 25 cm in diam., apex almost glabrous; bark gray, nearly smooth toward base of trunk. Leaves 25-45, 1-pinnate, 50-130 × 20-40 cm; petiole suborbicular in cross section, 10-40 cm, with 9-16 spines along each side throughout length, base densely brown tomentose; leaf blade ovate-oblong in outline, flat; leaflets in 40-70 pairs, longitudinally inserted 0.8-1.8 cm apart at 55-65° to rachis, straight, 10-17(-23) cm × 4-7(-9) mm, leathery, glabrous, midvein prominent on both surfaces, especially adaxially, base decurrent, margin flat or slightly recurved, apex attenuate, pungent. Cataphylls triangular-lanceolate, 4-7 × 1-1.3 cm, densely yellow-brown tomentose, apex long attenuate, subsoft at tip. Pollen cones conical-cylindric, 15-25 × 4-6 cm; microsporophylls cuneate or broadly cuneate, 1.5-2 × 0.6-1 cm; apical sterile part subrhombic, thickened, densely yellow or brown tomentose, margin subentire, with short, upcurved mucro. Megasporophylls 40-60, tightly grouped, 8-13 cm, densely yellowish brown silky tomentose; stalk 3-8 cm; sterile blade broadly ovate or flabellate, 5-6 × 4-8 cm, margin pectinate, with 17-35 lobes 2-3.8 cm, terminal lobe broadly lanceolate, 1.5-3.5 cm, margin irregularly serrulate or biserrulate; ovules 1 or 2 on each side of distal part of stalk, glabrous. Seeds 2-4, green to yellowish brown, broadly obovoid or subglobose, ca. 2 × 1.8 cm; sarcotesta not spongy or fibrous. Pollination Apr-May, seed maturity Oct-Nov.

Similar to Cycas siamensis Miquel in its gray and abruptly swollen trunk base, but quite different from that species in its strongly adaxially raised midvein and small seeds (ca. 1.8 cm in diam.) with sarcotesta not spongy or fibrous.

* Hills and rocky slopes among grass and low shrubs, or in open broad-leaved forests, with tropical climate of hot, wet summers and hot, dry winters; 600-800 m. Hainan (Changjiang Xian)