Moderate, clustered, unarmed, pleonanthic, monoecious palm. Stems erect, branching at the base and also aerially by forking, bearing leaf sheath remains distally, eventually becoming bare, marked with close leaf scars. Leaves pinnate, arranged in 5 vertical rows, marcescent or neatly abscising; sheaths tubular, soon disintegrating into an interwoven mass of fibres; apparent petiole short to elongate, adaxially channelled, abaxially rounded, glabrous, the margins bearing the remains of leaf sheath fibres, or becoming smooth; rachis ± straight or curved, adaxially channelled near the base, angled distally, abaxially rounded or flattened; leaflets numerous, single-fold, close, regularly arranged, except at the very tip, stiff, held in one plane, linear, the tips mostly asymmetrically 2-lobed, except at the leaf tip where acute or sometimes hooked, thinly glaucous, adaxial surface bearing scattered, minute, dot-like scales, abaxially with scattered dot-like scales, and a few large brown ramenta along the main vein, transverse veinlets conspicuous, sinuous. Inflorescences solitary, interfoliar, branching to 1 order, shorter than the leaves, protandrous; peduncle elongate, round in cross-section; prophyll short, tubular, 2-keeled, enclosed within the leaf sheaths, splitting apically; peduncular bract inserted near the prophyll, tubular and entirely enclosing the inflorescence until shortly before anthesis, later splitting longitudinally along the abaxial face and expanding, becoming cowl-like, woody, smooth, abaxially somewhat striate but not grooved, apically with a short, laterally flattened beak; rachis usually shorter than the peduncle, bearing numerous, spirally arranged, rather distant, spreading rachillae, each subtended by a low triangular bract; rachillae elongate, swollen at the very base and with a short or long basal bare portion, above which bearing few to numerous spirally arranged triads, Distribution of Jubaeopsis distally bearing paired or solitary staminate flowers; rachilla bracts and floral bracteoles small, inconspicuous. Staminate flowers rather large, perforate and micro-channelled, or perforate-rugulate, aperture margin asymmetrical, sessile; sepals 3, distinct, unequal, imbricate, ± triangular, similar; infratectum columellate; longest axis 63–81 µm [1/1]. Pistillate keeled; petals 3, distinct, very unequal, much larger than the sepals, flowers ovoid, only slightly larger than the staminate; sepals 3, distinct, boat-shaped with triangular tips, valvate; stamens (7–)8–16, filaments broad, rounded, with pointed tips, imbricate, somewhat irregularly slender, fleshy, ± cylindrical, apically inflexed, anthers linear, basally keeled; petals 3, distinct, ± twice as long as the sepals, broad, rounded, sagittate, dorsifixed, introrse; pistillode small, irregularly trifid. Pollen imbricate except at the short valvate triangular tips; staminodal ring ellipsoidal, frequently elongate, usually with either slight or obvious collar-like, very briefly toothed or consisting of several irregular tooth-asymmetry; aperture a distal sulcus; ectexine tectate, finely perforate, like lobes; gynoecium ± ovoid, trilocular, triovulate, stigmas 3, very short, ± triangular, ovules hemianatropous, laterally attached. Fruit 1-seeded, brown at maturity, globose with a short apical beak, stigmatic remains apical; epicarp smooth, mesocarp thin, fibrous, only slightly fleshy, easily separated from the endocarp at maturity, endocarp thick, bony, with 3 vertical grooves, the pores lateral just below the equator. Seed basally attached, somewhat irregular in shape, endosperm homogeneous with a large central cavity; embryo lateral, next to one of the endocarp pores. Germination remote tubular; eophyll entire, lanceolate. Cytology: 2n = 160–200.