Clustered robust palm climbing to 30 m, rarely to 50 m. Stems without sheaths 13-22 mm in diameter, with, 25-45 mm; internodes 14-25 cm long, commonly 15-18 cm. Leaf sheath lightly striate, light brown to mid-green, very sparsely and patchily armed with dark brown to glaucous black spines, often concentrated on the ocrea; sheaths often becoming bare with spines sloughing to leave raised, linear blister-like scars; thin white caducous indumentum present on young sheaths, absent on mature sheaths; ocrea saddle-shaped, with 1.5-2 cm. rounded lobe abaxial to the leaf, armed as the leaf sheath, spines concentrated on margin, extending for ± 2.5 cm; knee absent, although conspicuous horizontal rounded swelling visible beneath leaf. Spear leaf dull reddish brown, becoming green. Juvenile stems up to 10 m, with sheaths less than 2 cm in diameter, leaves strongly bifid, becoming pinnate, with a short (less than 6 cm) petiole, 30-45 cm long, 10-15 cm broad at the widest point, with 60-100 cm long cirrus emerging from the centre; elaminate rachis common at base of stem, 1.5-2 m long. Leaves on mature stems sessile, or with a short (less than 3 cm) flattened, unarmed petiole; rachis unarmed 1.2-2 m long, abaxially rounded, adaxially concave, becoming trapezoid then triangular in cross section distally, unarmed; cirrus 0.8-1.5 m long, rarely 2 m, unarmed; leaflets up to 30-50 on each side of the rachis, composed of a single fold, rarely rarely composed of up to 4-folds, linear-lanceolate or ± sigmoid, broadly to narrowly attenuate at base, finely acuminate at apex, 25-45 cm long, 2.2-3.3 cm broad at the widest point, ± pendulous, uni, bi or sometimes tri-nerved, armed along the margins with robust spines particularly at base of leaflet, lowermost leaflets smaller than the rest, arching and somewhat pendulous; acanthophylls up to 4 cm long. Inflorescences born in leaf axils ca. 3 m, from stem apex, peduncle up to 30 cm long, flattened, ± rectangular in cross section; prophyll up to 15 cm long; peduncular bracts ca. 4, 13-15 cm long, grey-brown without, crimson-brown within; rachis up to 1.8 m long, pendulous; rachis bracts as the peduncular bracts except increasingly triangular, acute, at apex; rachillae ± rounded or slightly flattened, 35-45 cm long, bracts dull crimson prior to anthesis; prophylls subtending flower cluster 4-6 mm long, somewhat striate. Flower cluster with 1 central pistillate flower subtended by 2 lateral cincinni with 1 pistillate and 3-4 staminate flowers. Flowers at anthesis not known. Fruit at maturity ± globose, 1.9-2.1 cm by 1.6-1.8 cm, with 17-19 rows of vertical scales. Seed smooth, sub-globose, 1.5-1.7 cm. by 1.2-1.5 cm. with linear cleft or rounded depression below; sarcotesta white, very thin (less than 0.3 mm).
Oncocalamus tuleyi occurs at the forest edge, adjacent to open areas, and in gap regrowth vegetation in forest. This species is an early coloniser of disturbed land and as such is a characteristic feature of roadside vegetation in logged forest. Although previously assigned to O. mannii, this species is clearly sufficiently morphologically distinct to warrant designation as a separate species. Oncocalamus tuleyi is characterised by very robust stems, large rachis bracts on the inflorescence, a uniform flower cluster arrangement and a smooth seed coat. Near threatened (NT) due to its restricted range and habitat loss, particularly along the Nigeria-Cameroon border.
Porijeklom iz, Cameroon, Nigeria
This species is restricted to coastal forest from SE Nigeria to SW Cameroon, north of the Sanaga River and is allopatric with O. mannii.