1	"Margins of pinnae revolute; pinnae narrow (mostly less than 4 mm wide)"	2
1	"Margins of pinnae flat or recurved; pinnae not revolute, more than 4 mm wide"	7
2	"Mature pinnae densely tomentose, at least beneath"	3
2	"Mature pinnae not densely tomentose"	4
3	"Pinnae numerous (210–410), narrow (2–4 mm wide), crowded (spaced at 4–6 mm on rachis), abruptly tapered apically"	"Cycas calcicola"
3	"Pinnae not as numerous (180–270), wider (4.5–6.5 mm wide), not crowded (spaced at 9–14 mm on rachis), gradually tapered apically"	"Cycas arenicola"
4	"Pollen cones fusiform, more than 35 cm long"	"Cycas pruinosa"
4	"Pollen cones ovoid or narrowly ovoid, less than 30 cm long"	5
5	"Pinnae green"	"Cycas arnhemica"
5	"Pinnae glaucous"	6
6	"Cataphylls soft"	"Cycas cairnsiana"
6	"Cataphylls pungent"	"Cycas desolata"
7	"Midrib of pinnae equally prominent above and below; pinna margins flat and not distinctly thickened"	8
7	"Midrib of pinnae not prominent above, very prominent below; pinna margins slightly to distinctly recurved, distinctly thickened"	12
8	"New growth strongly glaucous"	"Cycas canalis"
8	"New growth green or bluish green"	9
9	"Pinnae concolorous, partly amphistomatic, crowded"	"Cycas conferta"
9	"Pinnae ±discolorous, hypostomatic, well-spaced on rachis"	10
10	"Stem less than 12 cm diam.; seeds less than 38 mm long; cataphylls finely orange- and grey-tomentose"	"Cycas armstrongii"
10	"Stem more than 12 cm diam."	11
11	"Cataphylls densely orange-tomentose"	"Cycas lane-poolei"
11	"Cataphylls shortly pale brown-tomentose"	"Cycas xipholepis"
12	"Basal pinnae progressively reduced in size"	13
12	"Basal pinnae not progressively reduced in size"	16
13	"Ultimate basal pinnae progressively reducing and merging into spines"	14
13	"Ultimate basal pinnae progressively reducing but clearly separated from spines"	15
14	"Leaves keeled (angle between opposing pinnae 135° or less); pinnae inserted at 40–50° on rachis"	"Cycas furfuracea"
14	"Leaves flat (angle between opposing pinnae 180°); pinnae inserted at 70–80° on rachis"	"Cycas basaltica"
15	"Crown and cataphylls densely orange-woolly or -floccose"	"Cycas maconochiei"
15	"Crown and cataphylls shortly grey and orange-tomentose"	"Cycas arnhemica"
16	"Leaves keeled"	17
16	"Leaves flat"	26
17	"Cataphylls hard, pungent"	18
17	"Cataphylls soft, not pungent"	20
18	"Stems slender (less than 15 cm diam.); leaves short (70–110 cm); cataphylls short (to 7 cm)"	"Cycas megacarpa"
18	"Stems thick (more than 17 cm diam.); leaves long (usually more than 110 cm); cataphylls long (usually 7 cm or longer)"	19
19	"Pinnae to 6 mm wide; margins distinctly recurved"	"Cycas angulata"
19	"Pinnae more than 6 mm wide; margins slightly recurved"	"Cycas brunnea"
20	"New growth glaucous"	21
20	"New growth green"	23
21	"New growth with many white or grey trichomes"	"Cycas couttsiana"
21	"New growth with mostly brown or orange trichomes"	22
22	"Pinnae 6–7.5 mm wide; fronds keeled at 80–120°"	"Cycas ophiolitica"
22	"Pinnae 4.6–6 mm wide; fronds keeled at 45–60°"	"Cycas platyphylla"
23	"Crown and cataphylls densely orange-woolly or -floccose"	24
23	"Crown and cataphylls very shortly grey- to white-sericose"	25
24	"Megasporophyll apex 6–10 cm long, with 24–32 lateral spines 3–6 mm long; apical spine 12–16 mm long"	"Cycas yorkiana"
24	"Megasporophyll apex 5–5.5 cm long, with 22–24 lateral spines 1–4 mm long; apical spine 21–25 mm long"	"Cycas badensis"
25	"Megasporophylls 10–12 cm long; apex dilated, 38–50 mm wide"	"Cycas tuckeri"
25	"Megasporophylls 13–20 cm long; apex not dilated, 20–28 mm wide"	"Cycas semota"
26	"Pinnae more than 9 mm wide"	"Cycas silvestris"
26	"Pinnae less than 9 mm wide"	27
27	"Pinnae brown-tomentose beneath"	"Cycas arenicola"
27	"Pinnae glabrous beneath"	28
28	"Pinna margins slightly to moderately recurved"	"Cycas media"
28	"Pinna margins flat"	"Cycas orientis"