Areca unipa 学问
Solitary, slender tall palm to 12 m tall. Stem ca. 7.5 cm diam.; internodes 3-16 cm long, leaf scars 1-1.5 cm wide, not conspicuous, green near crown and dark to brownish grey near the base. Leaves 7 in crown, pinnate, ca. 119 cm long (including petiole); sheath tubular, ca. 54 cm long and ca. 7 cm wide, smooth, not fibrous, shiny cream to light green become dull green; crownshaft well defined, up to 75 cm long and up to 7 cm diam.; petiole ca. 16.5 cm long, slightly channelled adaxially, rounded abaxially; rachis slender, ascending but not arching, with adaxial longitudinal ridge, rounded abaxially; 9−10 leaflets on each side, more or less regularly arranged, spaced by 9-15 cm, basal leaflets ca. 42 x 1-4 cm, with 3 folds, sigmoid, middle leaflets 41-44 cm long, 1.5-2.5 cm wide at base and 7.5-11 cm wide at the tip, with 5 folds, sigmoid, terminal leaflet pair 14 cm long, 2-4 cm wide at the base and 4-7 cm at the tip, with 3-6 folds, broadly wedge-shaped to slightly cuneate, notched tips, the second and third leaflet pairs below the terminal pair splitting between the folds to about half way to the base, papery, discolorous, darker adaxially than abaxially. Inflorescence infrafoliar, slender, 30-40 cm long and 10-15 cm wide, protandrous, branching to 2 orders; prophyll elongated, slender, up to ca. 26 x 2 cm (very young stage), two-keeled, leathery, cream, light green near the apex; peduncle 1-4.5 cm long, green with numerous stellate hairs; rachis cream to yellowish green with thick rusty brown indumentum of stellate hairs; rachis bracts caducous; rachillae up to 21 cm long and 1-4 mm wide, slender, pale green, elongate and sinuous near the base; floral clusters distichous on rachillae, only one complete triad including female flower occurring at the base of each rachilla, remaining clusters comprising very few paired and solitary staminate flowers. Staminate flowers small, sessile, triangular, elongate or tear-drop shaped, 4.5-6 x 2.1-2.5 mm in bud, asymmetric; sepals 3, low, ca. 2.1-2.5 x 1.1-1.5 mm, united at the base; petals 3, triangular, elongate or spathulate, 4.2-5 x 2.1-3.5 mm, striate; stamens 6, small, 2.2-2.8 mm long and 1 mm wide; filaments thick, 0.9 mm long and 0.1-0.4 mm wide, darker than anther; anthers ca. 2.2 mm long and 0.6 mm wide, sagittate, longer than the filaments; pistillode longer than stamens, 2.5-3.2 x 0.8-1 mm, trifid. Pistillate flowers larger than the staminate, triangular, borne on the enlarged basal portion of rachillae, only one per rachillae, buds varying greatly in size depending on stage of development, 1.1 x 0.9 cm (in bud) to 2 x 1 cm (in late anthesis); sepals 3, strongly imbricate, ca. 1.5 x 0.9 mm in late anthesis, triangular, asymmetrical, striate; petals 3, imbricate, triangular, ca. 1.3 x 0.8 mm in late anthesis, striate; gynoecium 7-12 mm long and 3-5 mm; stigma ca. 3 mm long, pointed with 3 lobes, 0.3 mm long; style ca. 5-9 mm long; staminodal ring encircling gynoecium, 2 mm high, lacking differentiated staminodes. Fruit obovoid or ovoid with beak at the apex, 5.5-6 x 3.5-3.8 cm (unripe fruits), beak 4-6 mm long and 5-6 mm in diam.; epicarp smooth, shiny, dark green (unripe), mature fruits not seen; mesocarp fibrous, 0.5 cm thick, 1.5 cm thick at the base (below the seed); endocarp very thin, adhering closely to the seed. Seed obovoid, slightly flattened at base, ca. 3 x 2.2 cm (from unripe fruits); endosperm ruminate. Eophyl bifid.
A new Critically Endangered species in 2012 which is similar to Areca catechu and Areca mandacanii in habit and inflorescence structure, but differs by having fewer leaves in the crown, by the slender leaf rachis and relatively long petiole, and the sigmoid multifold leaflets and broadly wedge-shaped terminal leaflets. Known only from the type locality in PT Bima Cakrawala Nusantara (a coal mining company) concession area, close to Ayata village in East Maybrat District, Maybrat Regency in the central part of the Bird’s Head Peninsula, West Papua Province, Indonesia. In lowland peat forest at an elevation of about 200 m above sea level.