Pithecolobium diversifolium var. microphyllum Bentham in Martius, Fl. Bras. 15(2): 432. 1876. — "Habitat in inundatis Lagadisso ad Rio S. Francisco provinciae Bahiensis: Martius." — Holotypus, M n.v. — Reduced to typical P. diversifolium by Lewis, 1987: 179.

P. diversifolium sensu Bentham, 1875: 574; 1876: 432, t. CXI; Pithecellobium diversifolium sensu Lewis, 1987: 178, fig. 11(A,B).

Stiffly branched arborescent shrubs attaining 5(-?) m, armed at all nodes of long-shoots with stout, widely ascending, basally dilated stipular spines, the young stems and lf-axes pilosulous, either thinly or densely, with straight widely spreading pallid hairs to 0.3-0.5 mm, the firmly papery, moderately bicolored lfts either pilosulous on both faces, or only beneath, or glabrous- ciliolate, the capituliform fl-spikes of cream-colored flowers arising solitary in axils of diminished or rudimentary lvs of slender brachyblasts. Primary stipules 3-8 mm, persistent as stout spines along defoliate branches, those of fertile brachyblasts subulate or spinulose, <2 mm. Lf-formula i—ii/1 —2(—3), some primary lvs 12-16-foliolate but all or most lvs associated with fls exactly 4-foliolate; lf-stks 1-7 mm, at middle 0.4-0.7 mm diam, the interpetiolar segment, when present, shorter that true petiole; a shortly stipitate nectary 0.3-0.5 diam between each pair of pinnae and at tip of each pinna-rachis; rachises of the one or the further pinna-pair 2-9(-14) mm; lft-pulvinules 0.4-0.6 x 0.3-0.4 mm, scarcely wrinkled; lfts when more than one pair distally accrescent, the blades inequilaterally obovate, elliptic-obovate, or rarely elliptic-ovate from shallowly semicordate base, at apex either emarginate, or obtuse, or obtuse-mucronulate, the larger ones 14— 21 x 8-12 mm, 1.4-1.8 times as long as wide; venation pinnate, the gently porrect or almost straight, only slightly excentric midrib giving rise on each side to 3-5(-6) major and random intercalary secondary nerves, the former brochidodrome close within the plane margin, and sometimes to an open tertiary reticulum, the whole venation finely prominulous on both faces or only so beneath. Peduncles 7-20(-26) mm; capitula ±10-20-fld, the receptacle ±2-4 mm; bracts lanceolate or triangular-acuminate 0.8-1.5 mm, persistent; fls sessile, homomorphic, the perianth 5-merous, either pilosulous or silky-strigulose externally, the corolla often more densely so than the calyx; calyx campanulate, weakly 5-nerved, 1.4- 2.6 x 1-1.4 mm, the low-triangular teeth 0.2-0.45 mm; corolla gently dilated upward 7-9 mm, 3—5 times as long as calyx, the erect, ovate lobes 1.3—2.5 x 0.8—1.2 mm; androecium 22-36-merous, 17-30 mm, the stemonozone 0.6-1 mm, the tube 7-9 mm, nearly as long as or slightly exserted from corolla, a little thickened internally at base but disc not developed; ovary linear- ellipsoid 1.3-2 mm, attenuate at base into a stipe 2.6-3 mm, at early anthesis glabrous but becoming minutely papillate or puberulent following fertilization. Pods and seeds (few seen) apparently as in P. excelsum, the seed-aril whitish.

In caatinga thickets and spiny chaparral, mostly below 300 m, almost confined to the middle and lower basin of rio S. Francisco in Bahia and perhaps adj. Minas Gerais, Brazil, extending feebly N through W Pernambuco to the headwaters of rio Parnaiba in SW Piauí, to be sought in Alagoas. — Map 1. — Fl. V-VII(-?), perhaps intermittently following rains. — Brinco de sauim.

Pithecellobium diversifolium is distinguished from P. excelsum as much by the immense geographic discontinuity between them as by any macromorphological divergence. The leaf-formulae are the same, and both vary in pubescence of foliage, but P. diversifolium has rather stouter and stiffer branches, shorter peduncles, and tends to have more numerous flowers to the capitulum. Whether they are directly related or independently derived from P. unguis-cati cannot be determined at present, and for this reason they are maintained as distinct species.