Solitary palm tree. Stem erect, 10 m tall, ca. 12–20 cm diam., basally with a large root boss to ca. 45 cm diam., distally stem very conspicuously ringed with oblique leaf scars, new internodes densely covered with white caducous wooly indument; internode ca. 9–17 cm long. Leaves ca. 12–15 in crown, spirally arranged and spreading; leaf sheath plus petiole ca. 90–100 cm long × ca. 18–20 cm wide at the base, composed of finely-netted matting of fibers breaking away easily and leaving a finely fibrous margin on the apparent petiole, apparent petiole adaxially channeled and abaxially rounded and covered adaxially with wooly caducous indument; true petiole 6–8 cm long, ca. 3.1–4.4 cm wide and 1.5–2.2 cm thick at the base of the leaf blade; rachis 2.2–2.5 m long with ca. 100–140 pairs of leaflets distributed in clusters of 2–3 along the rachis in various divergent planes; middle leaflets ca. 80–90 cm long × 3–4 cm wide. Infloresence interfoliar, androgynous, erect in bud, later horizontal; peduncle 60–61 cm long × 4 cm wide × 2 cm thick; peduncular bract ca. 90–103 cm long including a beak 4–5 cm and the expanded or inflated part of the bract measuring ca. 55–65 × 27–29 cm and with a perimeter 33–37 cm, 5–9 mm thick, often separating from the peduncle before the fruits reach full maturity; rachis 49–52 cm long; rachillae ca. 70–100, apical ones ca. 54 cm long and basal ones ca. 118 cm, a major part of the distal portion of the rachillae devoid of any flowers, sterile and folded back and forth on themselves like dried noodles or worms. Flowers bright yellow drying white or cream-colored. Staminate flowers near the base ca. 9–10 mm long, sessile; sepals 3, distinct, triangular, imbricate but briefly connate at base, acute, membranaceous, glabrous; petals 3 distinct, unequal, obovate, valvate, fleshy, glabrous, with inconspicuous venation, ca. 8–9 × 4 mm, obtuse to broadly acute; stamens 6, distinct, 4–5 mm long, with filaments 1.5 mm long; pistillode trifid, less than 0.5 mm long. Pistillate flowers, conical, sessile; sepals glabrous, without visible venation, sclerenchymous or fleshy, imbricate, ca. 9–10 × 8–9 mm, acute, faintly keeled at tip; petals 3, distinct, imbricate at base, valvate at apex with valvate tip ca. 2–3 mm long, triangular, indistinctly nerved, glabrous, 11 × 8–9 mm, acute; gynoecium of receptive flower ovoid, 9 × 7 mm, covered in wooly tomentum, persisting on the apex of the fruit; stigmas 3, ca. 2 mm long; staminodal ring ca. 3 mm long, undulate with ca. 6 undulations and three small residual teeth, one on every other undulation. Fruits orange when mature, 5–6 × 4 cm, ovoid; cupule (persistent perianth) dark brown, ca. 2 cm in diam. × ca. 1 cm high; petals slightly longer than sepals; staminodial ring truncate, ca. 3 mm high × 10 mm diam.; epicarp smooth for most part but tomentose at apex; mesocarp fleshy, fibrous or pulpy remaining as a fibrous mat over endocarp; endocarp ovoid, 4.5–5 × ca. 3.5–4 cm, ca. 6 mm thick, hard, bony, brown to red-brown, apex with a distinctive, trilobed protuberance or beak, interior smooth, trivittate, slightly triangular in cross-section, outer surface nearly smooth, with small fibers, only slightly pitted, pores 3(–4) nearly even with surface, sutures visible especially at apex. Seed 1, elliptical, 3 × 2.5–3.2 cm; endosperm homogeneous. Germination remote tubular with cotyledonary tube penetrating deeply before sending up a plumule; eophyll simple, lanceolate.
In pre-Amazonian seasonally wet, marginal or secondary forests on terra firme with deep lateritic clay soils on rolling or steep hilly slopes at ca. 100–200 m. elevation. Often growing in open pastures. Also seen on lower slopes adjacent to river floodplains. Other palms present were Oenocarpus bataua, Oenocarpus disticus, Attalea maripa (Maxmiliana maripa) with Euterpe oleracea in the low lying areas. PHENOLOGY: Many of the trees in September had immature developing fruits. A small number had mature fruits and fewer still had flowers. Fortunately, I found a few sporadic inflorescences, but all contained only male flowers. I found this initially perplexing, but after growing them at MBC, it has been observed that the first few inflorescences of young palms do frequently produce only male flowers and often these flower outside their normal season. However, it must be noted that female flower bearing inflorescences were observed opening at MBC in September.