Key to species based on fruiting material
Note: the measurement of cupule height and diameter exclude perianth lobes.
1. Fruit perianth lobes entirely or partially persistent…..2
1. Fruit perianth lobes caducous……17
2. Fruit perianth lobes partially persistent, broken at upper half, leaving a truncate apex…..3
2. Fruit perianth lobes entirely persistent…..5
3. Mature leaves with dense curly hairs below (if becoming glabrescent the remnant of indumentum always present near the midrib)……1. C. angustitepalum
3. Mature leaves glabrous…..4
4. Lateral veins extending to 1/2–3/4 the lenght of leaf blade; twig-end with leaves opposite; cupule funnel-shaped, shallow, c. 2 mm high, c. 3 mm diameter; infructescence paniculate-cymose…… 2. C. burmannii
4. Lateral veins extending to the leaf tip or at the base of acumen; twig-end with leaves spirally arranged; cupule cup-shaped, thick, 6–7 mm high, c. 4 mm diameter; infructescence racemiform……18. C. racemosum
5. Fruit cupule enlarged, perianth lobes fleshy and thickly coriaceous, equal to or more than 0.5 cm long and partially covering the fruit…..6
5. Fruit cupule not enlarged, perianth lobes small, less than 0.5 cm long and covering the base of fruit…..7
6. Fruit perianth lobes plicate; fruit pedicel triangular in cross-section……5. C. crassinervium
6. Fruit perianth lobes not plicate; fruit pedicel terete in cross-section……12. C. lawang
7. Mature leaves blade hairy below……8
7. Mature leaves blade glabrous below……14
8. Mature leaves with straight and appressed hairs below, usually sparse……9
8. Mature leaves with curly hairs below, usually dense (if becoming glabrescent the remnant of indumentum always present near the midrib)……12
9. Mature leaves equal or more than 25 cm long …..10. C. kerangas
9. Mature leaves less than 25 cm long…..10
10. Midrib distinctly angular below; leaf apex caudate, abruptly constricted, forming a slender and appendage-like acumen ……19. C. rhynchophyllum
10. Midrib smoothly raised below; leaf apex when intact is acute, without acumen……11
11. Fruits cupule inconspicuous, very shallow, c. 1 mm high, c. 2 mm diameter; leaf hair to 0.2 mm long, straight and appressed……8. C. iners
11. Fruits cupule distinct, c. 4 mm high, 4–6 mm diameter; leaf hair 0.2–1 mm long, wavy or curly……23. C. subcuneatum
12. Major intercostal veins scalariform and as prominent as the midrib; minor intercostal veins scalariform……9. C. javanicum
12. Major intercostal veins subscalariform, not as distinct as midrib; minor intercostal veins reticulate……13
13. Leaf apex conspicuously acuminate, acumen 0.5–2 cm long; twig densely hairy, drying yellowish to greyish brown.……25. C. tahijanum
13. Leaf apex if intact is acute; twig glabrous, drying dark brown to blackish….. 23. C. subcuneatum
14. Mature leaves more than 30 cm long……. 7. C. grandifolium
14. Mature leaves less than 30 cm long……15
15. Lateral veins extending to 2/3–3/4 the lenght of leaf blade……26. C. verum
15. Lateral veins extending to the leaf tip or at least the base of acumen…..16
16. Leaf apex acuminate or acute with blunt tip, acumen to 1 cm long……16. C. politum
16. Leaf apex caudate, abruptly constricted, forming a slender and appendage-like acumen, (0.5–)1–3 cm long ……6. C. cuspidatum
17. Leaves penninerved; terminal bud perulate…..17. C. porrectum
17. Leaves trinerved or triplinerved; terminal bud not perulate…..18
18. Lateral veins extending to 1/2–3/4 the lenght of leaf blade……19
18. Lateral veins extending to the leaf tip or at the base of acumen……21
19. Mature leaves with dense curly hairs below (if becoming glabrescent the remnant of indumentum always present near the midrib)……11. C. kinabaluense
19. Mature leaves glabrous…..20
20. Fruit cupule crateriform, shallow, 2–3 mm high, 5–6 mm diameter. Habitat restricted to limestone…..3. C. calciphilum
20. Fruit cupule cup-shaped, deep, c. 6 mm high, 8 mm diameter. Habitat not restricted to limestone…..20. C. sintoc
21. Mature leaves hairy below (if becoming glabrescent, the remnant of indumentum always present near the midrib)……22
21. Mature leaves glabrous…..23
22. Fruit cupule cup-shaped, c. 4 mm high, c. 5 mm diameter…..24. C. sublanuginosum
22. Fruit cupule funnel-shaped, flattish, c. 1 mm high, c. 2 mm diameter……22. C. subavenium
23. Fruit cupule rim undulating, outer wall with faint longitudinal ridges…..14. C. pendulum
23. Fruit cupule rim not undulating, outer wall smooth.…..24
24. Fruit large, 1.5–2 by 1 cm; cupule large, 0.7–1 cm high, 1 cm diameter. Large tree to 40 m tall……21. C. soegengii
24. Fruit small, 0.5−1 by 0.3−0.5 cm; cupule small, c. 5 mm high, 5–8 mm diameter. Small to medium sized tree, to 12 m tall……25
25. Twig and petiole upon drying pale brownish, concolorous with the leaf blade……13. C. paiei
25. Twig and petiole upon drying black in colour, discolorous to the leaves blade…….26
26. Minor intercostal veins prominent and distinctly raised……4. C. corneri
26. Minor intercostal veins faint……15. C. percoriaceum