Thrinax Linnaeus f. ex Swartz (1788: 57)

Henderson, Andrew, 2023, A revision of Coccothrinax, Hemithrinax, Leucothrinax, Thrinax, and Zombia (Arecaceae), Phytotaxa 614 (1), pp. 1-115 : 99-100

4. Thrinax Linnaeus f. ex Swartz (1788: 57) .

Type:— Thrinax parviflora Swartz

Thrinax subgenus Euthrinax Drude (1889: 34) . Type:—Not designated.

Stems 4.0(1.5–18.0) m long and 10.9(5.0-24.0) cm diameter, solitary. Leaves more or less deciduous or only leaf bases persisting on stem; leaf sheaths split at the base; leaf sheath fibers 0.2(0.1–0.3) mm diameter, thin, flimsy, closely woven, forming ligules at the apices; petioles 12.6(5.7–30.2) mm diameter just below the apex; palmans 21.6(11.0–41.0) cm long, relatively long, without prominent adaxial veins; interfold filaments absent; leaf blades not wedge-shaped; segments 45(29–58) per leaf, the middle leaf ones 63.8(38.5–112.0) cm long and 3.3(2.2–4.9) cm wide; segments pendulous at the apices, giving a three-dimensional appearance to the leaf; middle leaf segments relatively long and narrow with a shoulder distal to the palman apex, widest at the shoulder, or relatively long and narrow without a shoulder distal to the palman, tapering gradually towards the apex, widest at palman apex; middle leaf segment apices attenuate; leaf segments not waxy or sometimes with a deciduous, thin layer of wax adaxially, without indumentum abaxially, with large, scattered, brownish scales on the abaxial surface, with well-developed transverse veinlets. Inflorescences erect, at least initially, amongst or above the leaves, with numerous partial inflorescences; rachis bracts swollen, woody, densely reddish-brown tomentose, or tubular, closely sheathing, membranous, brown tomentose; partial inflorescences 12(6–15); proximalmost rachillae straight, 8.6(4.5–14.0) cm long and 1.0(0.5–1.7) mm diameter in fruit; rachillae glabrous or granulose at or near anthesis; flowers spirally arranged; stamens 7(6–9), elongate, spreading irregularly at anthesis; anthers latrorse; fruit pedicels 2.4(0.6–5.0) mm long; fruits 5.9(4.4–7.1) mm long and 5.8(4.4–7.3) mm diameter, white or dull white; fruit surfaces smooth or sometimes with projecting fibers; seed surfaces smooth; seeds in longitudinal section intruded by the hilum more than half way, usually from base to apex, the apex of the intrusion narrowed.

Key to the species of Thrinax

1. Middle leaf segments 4.6(4.2–4.9) cm wide; rachis bracts swollen, woody, densely reddish-brown tomentose; proximalmost rachillae 11.0(9.5–14.0) cm long; eastern Jamaica............................................................................................................. T. excelsa

- Middle leaf segments 3.2(2.2–4.3) cm wide; rachis bracts tubular, closely sheathing, membranous, brown tomentose; proximalmost rachillae 8.4(4.5–12.7) cm long ....................................................................................................................................................... 2.

2. Middle leaf segments without a shoulder distal to the palman, tapering gradually towards the apex, widest at palman apex; pedicels 3.0(1.9–5.0) mm long; USA (Florida), Bahamas (North Cat Key), Mexico, Belize, Honduras, Cuba, Jamaica, Hispaniola ............ ............................................................................................................................................................................................. T. radiata

- Middle leaf segments with a shoulder distal to the palman apex, widest at the shoulder; pedicels 1.5(0.6–3.3) mm long; Jamaica. ......................................................................................................................................................................................... T. parviflora