1A. Calyx glabrous	2
1B. Calyx sparingly to densely puberulous or pubescent	7
2A. Leaflets 1–5 pairs per pinna	3
2B. Leaflets more than 5 pairs per pinna	5
3A. Leaflets 1–2 pairs per pinna (rarely 3 or 4); trunk usually with knobby prickles	6. S. nigrescens
3B. Leaflets 3–5 pairs per pinna; trunk usually without persistent prickles	4
4A. Pods (5–) 8–18 × 2–3.5 cm; apex acuminate or apiculate	4. S. goetzei subsp. goetzei
4B. Pods 5–7 × 0.8–1 cm; apex mucronate	5. S. modesta
5A. Calyx 0.75–1.25 mm long, red or purplish	6
5B. Calyx 1.5–3.5 mm long, normally not red or purplish	8. S. polyacantha subsp. campylacantha
6A. Inflorescence 1.5–3 cm long; leaflets 11–17 pairs per pinna	7.S. persiciflora
6B. Inflorescence (4–) 5–12 cm long; leaflets 12–45 pairs per pinna	3. S. galpinii
7A. Leaflets 3–10 pairs per pinna	1. S. burkei
7B. Leaflets 16–50 pairs per pinna	2. S. catechu