Stems clustered, short and subterranean, mostly obscured by persistent leaf bases. Leaves 6-20 per stem, pinnate, sometimes undivided, spiny; leaf sheaths open, not forming crownshafts, sheaths and petioles elongate, covered with flattened spines often in short rows or sometimes arranged in whorls completely encircling sheaths and petioles; pinnae sometimes silvery gray on abaxial surfaces, usually sigmoid, less often linear, regularly arranged and spreading in same plane or, more often, irregularly arranged and spreading in different planes, pinnae at apex usually joined in compound terminal pinna, sometimes this absent. Plants dioecious, most iteroparous, some semelparous. Inflorescences borne simultaneously in axils of reduced leaves on a short stem, this dying after flowering, in iteroparous plants inflorescences borne sequentially, emerging from a groove on outside of subtending leaf sheaths, inflorescences branched to 2 orders or sometimes spicate, covered with many persistent, sheathing bracts very short and spicate, short and branched, or very long, branched, and rooting at apex and forming new plants; in male inflorescences flowers borne in densely arranged pairs on short, thick rachillae; in female inflorescences flowers either solitary or borne in pairs with a sterile male flower, also densely arranged on rachillae. Fruits reddish brown, ovoid, obovoid, or pear-shaped, usually 3-seeded, covered with many overlapping scales, tips of scales turned up and giving fruit a spiny appearance; endosperm homogeneous; germination adjacent; eophylls bifid.
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