1 Leaves palmate or costapalmate (lacking a central axis or with a short central axis, the outline of the leaf blade about as long as wide); [subfamily Coryphoideae].

  2 Petioles unarmed (though the leaf sheaths are strongly armed with long needle-like spines in Rhapidophyllum hystrix).

    3 Leaves costapalmate (with a hastula extending at least several cm into the leaf blade, especially visible on the leaf underside); [tribe Sabaleae]

    3 Leaves palmate; [tribe Cryosophileae].

      4 Leaf sheaths bearing long (10-50 cm) needle-like spines; [c. peninsular FL northwards to SC, GA, AL, and MS]

      4 Leaf sheaths unarmed; [s. peninsular FL].

        5 Petiole not split at the base; fruit purple, turning black; inflorescence shorter than the leaves

        5 Petiole split at the base; fruit white; inflorescence longer than the leaves.

          6 Leaves glaucous on upper surface (adaxially); hastula (on upper surface) silky upon leaf emergence (but pubescence caducous); leaf blade composed entirely of palisade cells; flowers sessile or subsessile; petiole base developing secondary splits

          6 Leaves green on upper surface (adaxially); hastula (on upper surface) glabrous or glabrescent upon emergence; leaf blade composed of either mesophyll cells or both mesophyll and palisade cells; flowers pedicellate; petiole base with only the single, primary split

  2 Petioles armed with sharp broad-based sharp teeth or linear spines; [tribe Trachycarpeae].

             7 Petiolar teeth or spines > 2 mm long; tree (trunk erect); hastula visible only on upper surface of leaf.

               8 Petiolar armature of linear spines (bulbous at the base, but > 5× as long as the base is wide)

               8 Petiolar armature of broad-based sharp teeth (the teeth 1-3× as long as the base is wide).

                 9 Trunks clustered, 5-15 cm in diameter, to 6 m tall

                 9 Trunks solitary, > 20 cm in diameter, to 22 m tall.

                   10 Petiole split at base; leaf segments with marginal fibers

                   10 Petiole not split at base; leaf segments lacking fibers; [subtribe Livistoninae]

                     11 Inflorescence having one main axis (with 3 orders of branching); mature fruits blue-green

                     11 Inflorescences having 3 main axes (3-forked at the base, each of the 3 main branches with 4 orders of branching); mature fruits orange

1 Leaves pinnate or bipinnate (with a well-developed central axis, the outline of the leaf blade much longer than wide).

                       12 Leaves bipinnate (when well-developed, smaller leaves or leaves of small plants may be merely pinnate); leaf segments cuneate, widening to an irregular and raggedly toothed tip; ["fishtail palms"]; [subfamily Arecoideae; tribe Caryoteae]

                       12 Leaves pinnate; leaf segments linear.

                          13 Leaf segments induplicate (V-shaped in ×-section, the midrib lowest, like the keel of a boat); [subfamily Coryphoideae; tribe Phoenicinae]

                          13 Leaf segments reduplicate (Λ-shaped in ×-section, the midrib highest, like the summit of a pitched roof)

                            14 Petioles armed with either teeth or needle-like spines.

                              15 Petiole backs armed with mostly spreading or descending, straight, black, needle-like spines; [subfamily Arecoideae; tribe Cocoseae; subtribe Bactridinae]

                              15 Petiole margins armed with stout-based straight or curved teeth (derived from modified leaflets), ascending towards the leaf apex at an obtuse angle, green, tan, or brown.

                                16 Stem to 6 m tall, not bulging near the middle; stem ridged with circumferential leaf scars; fruits globose, to 2.5 cm long, orange when ripe; leaflets on each side of rachis in a single plane, the two sides angled upwards, giving the leaf a V-shaped ×-section; [subfamily Arecoideae; tribe Cocoseae; subtribe Attaleinae]

                                16 Stem to 15 m tall, sometimes bulging near the middle; stem covered with woody, roughly triangular leaf scars; fruits ovoid, 3.4-5 cm long, black or red when ripe; leaflets on each side spread in 2 or more planes, giving the leaf a plumose appearance; [subfamily Arecoideae; tribe Cocoseae; subtribe Elaeidinae]

                            14 Petioles unarmed.

                                  17 Shrubs, with stems 1-2 cm in diameter and to 3 m tall; fruits 0.6-0.8 cm in diameter; dioecious, male flowers and female flowers on different plants; [subfamily Arecoideae; tribe Chamaedoreeae].

                                  17 Trees, with stems > 10 cm in diameter and > 5 m tall when mature; fruits > 1 cm in diameter (except Roystonea, with fruits 0.7-0.8 cm in diameter); monoecious (with unisexual flowers) or hermaphroditic (with bisexual flowers).

                                    18 Trees without crownshafts (a structure made up of the sheathing bases of the living leaves, extended vertically at the top of the trunk but below the apparent crown, usually smoother and more brightly colored, such as green or reddish, than the trunk); [subfamily Arecoideae; tribe Cocoseae; subtribe Attaleinae].

                                       19 Leaves with leaflets arrayed in one plane on either side of the rachis; fruit hard and dry, > 10 cm in diameter

                                       19 Leaves with leaflets arrayed in 2 or more planes on either side of the rachis; fruit fleshy, 2-3 cm in diameter

                                    18 Trees with crownshafts (a structure made up of the sheathing bases of the living leaves, extended vertically at the top of the trunk but below the apparent crown, usually smoother and more brightly colored, such as green or reddish, than the trunk).

                                         20 Large trees, with trunks 40-60 cm in diameter, to 30 m tall; fruits 0.8-1.3 cm in diameter; trunks solitary; [subfamily Arecoideae; tribe Roystoneeae]

                                         20 Smaller trees, with trunks 5-30 cm in diameter, to 10 m tall; fruits 1.0-3.5 cm in diameter; trunks either solitary or clumped.

                                           21 Stems to 12 cm in diameter, either clustered or solitary; trunk with either well-spaced or close circumferential leaf scar ridges; [subfamily Arecoideae; tribe Areceae].

                                             22 Leaf segments acuminate at tip; leaf sheath yellowish; endocarp circular in ×-section; [subtribe Dypsidinae]

                                             22 Leaf segments jagged or irregular at tip; leaf sheath green; endocarp 5-lobed in ×-section; [subtribe Ptychospermatinae]

                                           21 Stems to 30 cm in diameter, solitary; trunk with closely spaced (< 5 cm apart) leaf scars

                                               23 Crownshaft tight, elongate, and bright green; fruits 2.5-3 cm in diameter; [subfamily Arecoideae; tribe Areceae; subtribe Ptychospermatinae]

                                               23 Crownshaft open, short, and gray-green; fruits 1-2 cm in diameter; [subfamily Ceroxyloideae; tribe Cyclospatheae]