Dwarf to large, solitary or clustered, hapaxanthic, monoecious or ?dioecious, acaulescent, shrubby or tree palms. Stem with congested or elongate internodes, usually obscured by persistent fibrous leaf bases and sheaths. Leaves spirally or distichously arranged, induplicately imparipinnate, marcescent; sheath covered in a great variety of tomentum, scales and hairs, often extended beyond the petiole to form a ligule, eventually disintegrating into a mass of black fibres; petiole well developed, slender to robust, ± circular in cross-section or channelled adaxially, rounded abaxially, covered in a variety of scales and tomentum; rachis angled adaxially, rounded abaxially, variously tomentose; leaflets single-fold except for the terminal flabellum, regularly arranged or grouped and fanned within the groups, linear-lanceolate, irregularly rhomboid or deeply lobed, sometimes auriculate at base, the distal margins praemorse, the veins parallel to the fold or radiating from the base, or ± pinnately arranged along the fold, adaxial blade surface glabrous, abaxial surface usually densely covered in pale indumentum and scattered bands of brown scales, transverse veinlets obscure. Inflorescences axillary, interfoliar, solitary, bursting through leaf sheaths, produced in a basipetal sequence, branching to 1 order only, unisexual, usually dimorphic, the pistillate usually the most distal or ‘terminal’, with inconspicuous bracts, the staminate proximal (lateral), often hidden by very conspicuous bracts; peduncle ± circular in cross-section, usually densely covered with indumentum; prophyll small, 2-keeled, tubular only at the very base; peduncular bracts several, ± spirally arranged, much larger than the prophyll, tubular at the very base, splitting, usually densely covered in brown scales and tomentum; rachis usually longer than the peduncle; rachis bracts minute; rachillae numerous, rather slender, ± spirally arranged, usually densely covered with indumentum, bearing spirally arranged, minute bracts, subtending flowers. Staminate flowers paired or solitary, sometimes accompanied by the rudiments of a central pistillate flower; calyx tubular, truncate, with 3 lobes or teeth; floral receptacle elongate and stalk-like between calyx and corolla; corolla much exceeding the calyx, tubular near the base, with 3, elongate, valvate lobes distally; stamens 3–15, the filaments united basally in a short to long column, adnate partially or completely to the corolla tube, sometimes partly adnate to the lobes, anthers linear, apically obtuse or acute; pistillode absent. Pollen ellipsoidal, ± bi-symmetric; aperture a distal sulcus; ectexine intectate, usually spiny, spines attached to smooth upper surface of foot layer, in some species spines more numerous along aperture margins, less frequently clavate, bases of clavae often swollen; longest axis 24–27 µm [4/7]. Pistillate inflorescence usually erect, with fewer, more robust rachillae. Pistillate flowers solitary, spirally arranged, each subtended by a low bract and surrounded by 3 bracteoles; sepals 3, low, rounded, imbricate, ± distinct or joined briefly at base, petals 3 united basally to about middle, valvate distally; staminodes 0–3; gynoecium ± globose, 2–3 locular, 2–3 ovulate with a conical apical stigma, ovules inserted adaxially at the base, hemianatropous. Fruit ellipsoidal, small, reddish or purplish, 1–2, rarely 3-seeded, stigmatic remains apical; epicarp smooth, mesocarp fleshy, filled with irritant needle-like crystals, endocarp not differentiated. Seeds basally attached, ellipsoidal or hemispherical, endosperm homogeneous; embryo lateral. Germination remote-tubular; eophyll ovate to elliptic with erose margins. Cytology: 2n = 32.
Dwarf to moderate, solitary or clustered monoecious pinnate-leaved palms from mainland Asia to southern Thailand, distinctive in the induplicate leaflets with praemorse tips, flowers borne in triads, very similar to Arenga but with united sepals in the staminate flower and always basipetal hapaxanthic.
Nine species, from the Nepal Himalayas and upper Burma to China and southwards to peninsular Thailand. Found in humid tropical forest from near sea level to 2000 m altitude; the genus becomes rarer southwards in Thailand, suggesting that it is adapted to cooler or more seasonal climates than those found in Peninsular Malaysia.