Key based on fruiting specimens (excluding Mucuna hirtipetala and M. incurvata for which no fruit was seen)

1	Mature leaves abaxially with dense pale silky hairs conspicuously sparser on primary veins; legume length 4-6 × width, surface without lamellae		(2)
+	Mature leaves glabrous or variously hairy with hairs at least as dense on veins; legume often relatively wider and/or with surface lamellae		(3)
2 (1)	Terminal leaflet narrow (length:width ratio (2-)2.5:1), apex with very well-marked 1-2 cm acumen, ca. 2 mm wide for most of length, abaxial hairs adpressed, ca. 1 mm; legume ± woody or thickly leathery, more than 12 cm, silky hairy.		5 M. calophylla
+	Terminal leaflet relatively broad (length:width ratio 1.25-1.75:1), apex with acumen absent or rarely to 5 mm, abaxial hairs often erect, shorter; legume fleshy, less than 10 cm, with irritant bristles.		18 M. bracteata
3 (1)	Legume without lamellae, sometimes wrinkled on surface or with winged margins		(4)
+	Legume surfaces each with 8-16 conspicuous obliquely transverse lamellae		(12)
4 (3)	Legume linear, often torulose, woody, usually at least 30 cm when mature		(5)
+	Legume either broadly oblong or small and fleshy, or if linear and ± woody then always less than 16 cm when mature		(8)
5 (4)	Legume margins each with a pair of thick woody wings ± evenly 3-5 mm wide and with definite edges, legume markedly torulose, each segment ± oval with rounded apex and base.		1 M. birdwoodiana
+	Legume margins not winged, at most wrinkled into irregularly thickened ridge to 2 mm wide and then legume not torulose, segments ± rectangular in outline		(6)
6 (5)	Legume glabrous, not torulose, only slightly swollen around seeds, segments ± rectangular, apical and basal edges ± straight; leaflets broadly rounded abaxially with dense short pale soft spreading hairs.		2 M. bodinieri
+	Legume glabrous or with dense short erect red-brown pubescence, markedly torulose, width at septa between seeds usually 1/2-2/3 width at widest point; leaflets acute or acuminate, abaxially often glabrous or sparsely hairy or with red-brown hairs		(7)
7 (6)	Mature legume without firm rounded raised margin, surface wrinkled or with coarse raised rugose-reticulate patterning, often without fine hairs; leaflets with fine reticulate venation, partially visible, clearly distinct from coarser reticulation, indumentum sometimes dense.		3 M. macrocarpa
+	Mature legume surface with firm rounded raised margin, surface with rather fine conspicuous but shallow reticulate patterning, and fine hairs; leaflets with reticulate venation fine and prominent, coarse reticulation often hardly distinct from fine, indumentum never dense.		4 M. sempervirens
8 (4)	Mature legume 2-3 × as long as wide, never less than 4 cm wide, leathery, with marginal wing 5-7 mm wide, surface glabrous or sparsely hairy with fine and regular reticulate pattern of raised lines giving a pitted appearance.		6 M. gigantea
+	Mature legume at least 4-6 × as long as wide, fleshy or leathery, margin sometimes thickened and sometimes longitudinally ridged but never winged, surface often hidden beneath dense hairs, where visible wrinkled or with irregular much coarser patterning of raised lines, never apparently pitted		(9)
9 (8)	Mature legume ± woody or thickly leathery, 13-15 cm, surface clearly visible beneath covering of short erect hairs and longer caducous irritant bristles; terminal leaflet 2-2.5 × as long as wide, apex with distinct long narrow acumen 1-2 cm; lateral veins curving more sharply and becoming indistinct or looping and joining near margin.		5 M. calophylla
+	Mature legume fleshy, 5-9 cm, surface usually nearly invisible beneath dense covering of silky hairs or caducous irritant bristles; terminal leaflet usually ca. 1.5 × as long as wide, apex acute or with short broad acumen to 0.5 cm; lateral veins uniformly straight or slightly curved, clearly reaching margin		(10)
10 (9)	Legume with pale silky hairs, not rigid or irritant; calyx with short pale hairs, rarely also with a few longer hairs but without longer irritant bristles.		16 M. pruriens
+	Legume with dense ferruginous or brown rigid caducous irritant bristles; calyx with short brown hairs and often longer irritant bristles		(11)
11 (10)	Lower 1/3 of infructescence axis always without fruit but with bract scars or with persistent bracts; leaflets quite thickly papery or ± leathery, markedly discolorous, abaxially pale greenish gray in dry state, midrib and veins conspicuously prominent, dark and less pubescent than rest of surface.		18 M. bracteata
+	Infructescence axis either with fruit throughout length or without fruit or scars in lower part; bracts all caducous before flowers open; leaflets much thinner, papery or membranous, abaxially not or only slightly paler, veins neither prominent nor dark and less pubescent than rest of surface.		16 M. pruriens
12 (3)	Stem (at least when young), petiole, and leaves abaxially with conspicuous soft ferruginous hairs; legume over 16 cm when mature; torulose.		13 M. championii
+	Stem, petiole, and leaves glabrous or with sparse pale hairs; legume size and shape various		(13)
13 (12)	Legume relatively small and narrow, to 10 cm, ca. 4 × as long as wide, margins ± parallel, marginal wings to 4 mm wide		(14)
+	Legume length only 2-3 × width, or if relatively narrow then legume much larger, at least 16 cm or at least with one margin convex, or marginal wings 1 cm or more wide		(15)
14 (13)	Legume with septa clearly visible as marked indentations; seeds almost spherical; terminal leaflet broadly triangular-cordate, 12-15 cm, base cordate.		15 M. cyclocarpa
+	Legume with septa just visible as indefinite indentations; seeds markedly laterally flattened, to 1/2 as thick as long; terminal leaflet rhombic-ovate, 6-13 cm, base cuneate.		14 M. lamellata
15 (13)	Legume lamellae erect, 2-winged along their margins to give T-shaped cross section, all lamellae clearly interrupted along midline of legume		(16)
+	Legume lamellae often partly adpressed, each a simple raised flap not dividing to give T-shaped cross section, sometimes erratically discontinuous, joined or branched near middle of legume but not creating a longitudinal midline		(17)
16 (15)	Legume (1 or)2-seeded, 6-9 × 4-4.5 cm, lamellae 8-12 per valve, with strongly revolute apical halves, marginal wings strongly inrolled; bracts never persistent; hairs on inflorescence axis and calyx erect, very short, 0.1-0.2 mm, velvety.		8 M. revoluta
+	Legume 3-seeded, 13-14 × 6-7 cm, lamellae ca. 18 per valve, with spreading or ± upcurved apical halves, marginal wings ± flat; some bracts large and conspicuous, often persistent to fruiting stage; hairs on calyx and inflorescence axis adpressed, 0.4 mm or more.		7 M. interrupta
17 (15)	Legume to 2 × as long as wide, oblong, usually asymmetric, often with both sides convex, never parallel		(18)
+	Legume 3-4 × as long as wide, linear or slightly curved, sides ± parallel in outline (swollen around seeds or not)		(19)
18 (17)	Legume with at least some lamellae joined or branched near middle of legume; basal and sometimes apical 1/2 of terminal leaflet with rather straight outline.		9 M. membranacea
+	Legume lamellae never branched, only a few short or discontinuous; terminal leaflet with very rounded outline.		12 M. hainanensis
19 (17)	Legume 2-2.5(-3) cm or less wide; leaflets with rather straight outline, terminal leaflet rhombic or rhombic-ovate.		14 M. lamellata
+	Legume 4 cm or more wide; leaflets with rounded outline, terminal leaflet elliptic or slightly obovate		(20)
20 (19)	Wings on lower (abaxial) margin of legume 0.5(-0.8) × as wide as those of upper (adaxial) margin; terminal leaflet 13-15 × 7.5-8.5 cm.		10 M. macrobotrys
+	Wings along both margins of legume ± equal in width; terminal leaflet 4.5-10.5(-16) × 2.5-6(-9) cm.		12 M. hainanensis