Robust, solitary, unarmed, pleonanthic, dioecious, tree palm. Stem erect, ringed with close leaf scars. Leaves induplicately costapalmate, marcescent, or falling under their own weight; sheath soon becoming open, densely tomentose, later with a conspicuous triangular cleft below the petiole, margins fibrous; petiole well developed, flattened adaxially, rounded abaxially, the margins armed with widely spaced coarse, forward-pointing spines, mostly in the mid-section; hastulae absent; costa short, more conspicuous abaxially than adaxially; blade divided ± regularly along adaxial folds to ca. 2/3 its length into single-fold segments, these further divided for a very short distance along abaxial folds, interfold filaments persistent at the adaxial sinuses, surfaces ± glaucous, with scattered dot-like scales, particularly along the ribs on the abaxial surface, longitudinal veins crowded, transverse veinlets obscure. Inflorescences interfoliar, becoming pendulous; prophyll and peduncular bracts, if any, not seen; rachis bracts tubular, with scattered caducous scales, and a long triangular limb; first-order branches ± pendulous, devoid of bracts except at the tip, margins sharp, the surfaces bearing scattered caducous scales, staminate inflorescence with first-order branches bearing at their tips 1–7 digitately displayed rachillae, in the pistillate bearing a single rachilla; rachillae catkin-like, bearing a tight spiral of rounded, densely hairy, imbricate bracts, connate laterally and to the axis to produce pits, filled with a dense pile of hairs. Staminate flowers borne in threes, each bearing a spathulate membranous bracteole included within the pit, the flowers exserted and exposed one by one from the pit; calyx stalk-like at the base with 3 narrow, spathulate, membranous, striate lobes with irregular margins; corolla with a conspicuous stalk-like base almost as long as the calyx lobes, bearing at its tip 3 oblong, membranous, striate, ±circular lobes; stamens 6, borne at the base of the corolla lobes, filaments elongate, tapering, anthers medifixed, apparently versatile, latrorse; pistillode 3-lobed, small. Pollen ellipsoidal, slightly asymmetric; aperture a distal sulcus; ectexine tectate, coarsely perforate-rugulate, aperture margin slightly finer; infratectum columellate; longest axis 36–49 µm [1/1]. Pistillate flowers solitary, borne on a short, densely hairy pedicel, lengthening after fertilisation; sepals 3, distinct, imbricate, obtuse, broad, membranous, glabrous, striate; petals 3, similar to the sepals; ?staminodes; gynoecium globose, with 3 eccentric, short, recurved stigmas, ovule probably orthotropous. Fruit ovoid, borne on the elongated pedicel, usually developed from only 1 carpel, rarely from 2 and then bilobed, with basal stigmatic remains, perianth whorls persistent; epicarp smooth, shiny, marked with scattered lenticels, mesocarp moderate, apparently ± dry at maturity, with ± radiating short fibres embedded in soft parenchyma, endocarp rather thin, crustaceous. Seed basally attached, ± broad, ellipsoidal, endosperm with a central hollow, conspicuously ruminate, the ruminations radial; embryo apical. Germination remote-tubular; eophyll entire, lanceolate. Cytology not studied.
Two species have been described, Medemia argun and M. abiadensis, the latter differing in its smaller fruit. Boulos (1968) records variation in fruit size in Egypt and most authors have, since Beccari, accepted one species only, M. argun. It occurs in desert oases. Gibbons and Spanner (1996) suggest that the habitat of M. abiadensis appears to differ from that of M. argun, and that the recognition of a single species may require reassessment.