Thrinax, Linnaeus f. ex Swartz, 1788

Henderson, Andrew, 2023, A revision of Coccothrinax, Hemithrinax, Leucothrinax, Thrinax, and Zombia (Arecaceae), Phytotaxa 614 (1), pp. 1-115 : 8

Key to the genera of the Thrinax unit

The five genera can be distinguished using the following key. This reflects the relationships of the genera as given by Cano et al. (2018).

1. Leaf sheaths split at the base; seed surfaces smooth or shallowly lobed; seeds in longitudinal section with a basal intrusion of the hilum ................................................................................................................................................................................................ 2.

- Leaf sheaths not split at the base; seed surfaces deeply lobed, the lobes running from base of seeds almost to apices, or lobed, the lobes running from base of seeds approximately to equator; seeds in longitudinal section without a basal intrusion of the hilum ... .......................................................................................................................................................................................................... 4.

2. Leaf segments with large, scattered, brownish scales on the abaxial surface; seeds in longitudinal section intruded by the hilum more than half way, usually from base to apex; Florida, Bahamas, Cuba, Hispaniola, Jamaica, Yucatan Peninsula, Honduras....... ................................................................................................................................................................................................ Thrinax

- Leaf segments with close rows of small, whitish dots between the veins on the abaxial surface, together with fewer, larger, scattered brownish or greenish scales; seeds in longitudinal section intruded by the hilum from base to about half way ............. 3.

3. Interfold filaments present; stamens short, forming a compact ring around the gynoecium at anthesis, the anthers extrorse; Cuba. ........................................................................................................................................................................................ Hemithrinax

- Interfold filaments absent; stamens elongate, spreading irregularly at anthesis, the anthers latrorse; Florida, Bahamas, Cuba, Puerto Rico, Hispaniola, western Lesser Antilles .................................................................................................................... Leucothrinax

4. Leaf sheath fibers stout, woody, forming a ring of reflexed spines at the sheath apex; flowers alternately and distichously arranged; fruits white; Hispaniola ......................................................................................................................................................... Zombia

- Leaf sheath fibers flimsy or stout, sometimes forming erect spines at the sheath apex; flowers spirally arranged; fruits seldom white; throughout the Caribbean .................................................................................................................................. Coccothrinax