Pithecolobium basijugum sensu Ducke, 1949: 45.

Slender, multifoliolate, cauliflorous trees (5-)6-20 m with smooth terete trunk to 1.5(—?) dm dbh, the young branchlets and all lf-axes pilosulous with straight, erect or widely incurved-ascending, yellowish or sordid hairs to 0.2-0.5 mm, the lvs bicolored, the thin-textured lfts dull olivaceous above, paler beneath, the inflorescence composed of short efoliate pseudoracemes of few-fld capitula arising from knots on annotinous and older wood ±1 m from the ground and upward. Stipules deltate-triangular, 0.5-1.3 x 0.3—0.75 mm, the blade thin-textured glabrescent, faintly 1-nerved or nerveless, tardily deciduous. Lf- formula (iv-)v-ix/(-14)16-22; lf-stks of larger lvs 6-15 cm, the petiole reduced to the pulvinus or almost so, the longer interpinnal segments 10-27 mm; a sessile, shallowly cupular thick-rimmed or almost plane buttonlike nectary 0.7-1.5 mm diam between the first pair of pinnae, somewhat smaller ones between 1-2 furthest pairs, and much smaller ones on pinna-rachises between the furthest 1-4 pairs of lfts; the pinnae strongly decrescent proximally, the first pair very short and loosely amplexicaul, the rachis of further ones 5-9 cm, the longer interpinnal segments 3-7 mm; lfts decrescent near each end of rachis, otherwise subequilong, all subsessile against the rachis, the pulvinule obsolete or almost so, the blades narrowly oblong from obliquely truncate base, shallowly sigmoidally arcuate, sharply auriculate postically, deltate-acuminulate at apex, the larger ones 11-17 x 3-5 mm, 3.1-4-(-4.4) times as long as wide; venation slenderly palmate and pinnate, the midrib subcentric, the inner posterior primary nerve produced to or beyond midblade, the outer one very short, the secondary nerves from midrib faint, the tertiary venules immersed. Primary axis of pseudoracemes 1.5-6.5 cm, 3-several-capitulate, the individual peduncles 2-9 mm, each subtended by a small deflexed bract charged ventrally with a buttonlike nectary about as wide, the capitula 4-10-fld, the receptacle 1-2 mm; bracts ovate ±1-1.5 mm, persistent; perianth (4—)5-merous, puberulent overall, the corolla greenish or ochroleucous, the filaments white; calyx campanulate, including the solid base 1-2 x 1.2-1.8 mm, the depressed-deltate teeth ±0.1 mm; corolla slenderly tubular, moderately dilated at the limb, 9.5-14 mm, the often unequal ovate lobes 1.4-1.8 mm; androecium 46-60-merous, 23-30 mm, the stemonozone 1.2-3.5 mm, the tube 1.2-1.9 mm; disc 0; ovary sessile, linear 2-2.8 mm, obliquely attenuate into the style, either glabrous or puberulent at anthesis. Pods 1-2 per capitulum, sessile or shortly attenuate at base into a pseudostipe, in profile linear, nearly straight, 12-26 x 1.1-1.5 cm, planocom-pressed becoming low-convex over each seed, when well fertilized (10-)12-16-seeded, the firmly leathery castaneous glabrous valves framed by dilated puberulent, almost straight or shallowly undulate sutures, becoming coarsely venulose, the endocarp not septiferous between seeds, resinous in each seed-locule; dehiscence follicular, through the ventral suture, the valves narrowly gaping; seeds well spaced along the pod-cavity, basipetal on short funicle, compressed-ellipsoid, in broad view 11-12 x 6-7 mm, the papery, dull brown testa girdled with a prominulous nerve, medially fuscous, lacking pleurogram; endosperm 0, the testa closely investing but free from the embryo.

In rain forest, on sandy and sandy-clay soils, mostly below 200 m but at its W limit in Peru at ±500 m, scattered along some upper tributaries of the Amazon River within 60°-78°W, 3°-9°S in depts. Amazonas and Loreto, Peru, and state of Amazonas, Brazil. — Map 21. — Fl. VIII-XII. — Pashaco, sacha-bubinsana (Peru).

Ducke (1949, l.c..) distinguished this species from Z. claviflora principally by its white filaments, but the small, almost nerveless stipules, the deltately acuminulate leaflets, the extended axis of the pseudoracemes, and the broader pods (11-15, not ±7.5 mm diam) are more substantial differences.