Lanonia tenuisecta Henderson & Nguy

Henderson, Andrew & D ựng, Nguy ễn Qu ốc, 2022, A revision of Lanonia (Arecaceae, Coryphoideae, Livistoninae), Phytotaxa 532 (3), pp. 209-245 : 239

18. Lanonia tenuisecta Henderson & Nguy ễn Quốc Dựng sp. nov. Type:— VIETNAM. Khanh Hoa province, Dien Khanh district, Hon Ba Nature Reserve , 12.116N 108.950E, 1,290 m, 11 July 2010, A. Henderson, Bui Van Thanh & Nguyen Thi Bich Ngoc 3707 (holotype HN!, isotype NY!). Fig. 18 .

Stems 1.4(1.0–2.8) m long, 2.2(1.8–2.5) cm diameter, solitary. Leaves 12; ligules 32.9(29.5–40.0) cm long, papery, not disintegrating into fibers; sheaths and proximalmost part of petioles with dense, flat, black scales; petioles 42.1(35.0– 60.0) cm long, 0.3(0.3–0.4) cm wide at the apex; petiole thorns usually stout, reddish-brown or dark brown, some bifid or often some in pairs, on proximalmost part of petiole; hastulas flat, rounded, not infolded; leaf blades 53.3(44.0– 70.0) cm wide; costas 2.9(1.8–4.0) cm long, triangular, with a pulvinus at the apex abaxially, with the numerous (rarely few) segments free almost to the base; segments 13(10–15) per leaf, not mottled, with minute, reddish-brown scales abaxially, with (on dried specimens) ruffled margins; middle segments 31.0(24.5–37.5) cm long, 2.2(1.4–3.0) cm wide at the apex; apices of middle segments with adaxial splits much deeper than abaxial ones. Inflorescences 85.0 cm long; prophylls 26.5(12.0-37.0) cm long; peduncles 57.0(44.5–70.0) cm long; rachis bracts narrowly tubular, splitting apically, not or sparsely tomentose; rachillae filiform, sparsely to moderately covered with short, mostly simple, brownish hairs; staminate rachises absent; staminate partial inflorescences 1, branched to 3 orders; staminate rachillae 34, 6.0 cm long, 0.3 mm diameter; staminate flowers 1.7 mm long; sepals not pedicellate at the base, not densely hairy; petals rounded at the apex; stamens with alternately long and short filaments and small, almost square anthers; filaments not elongate; pistillodes undivided; pistillate rachises absent; pistillate partial inflorescences 1, branched to 2 orders; pistillate rachillae on proximalmost partial inflorescence 3(2–4), 13.1(10.0–16.2) cm long, 1.0(0.8–1.1) mm diameter; pistillate flowers 2.5 mm long, with short styles; fruits 7.6(7.4–7.7) mm long, 7.3(7.1–7.4) mm diameter, globose, white, with rough, pebbled surfaces; seeds with a straight basal intrusion.

Distribution and habitat:—Southern Vietnam in Khanh Hoa province, known only from Hon Ba Nature Reserve, in montane rainforest at 1,449(1,250 -1,578) m elevation ( Fig. 17 ).

Taxonomic notes:— Six s pecimens formerly included in Lanonia hexasepala (see notes under that species) differ from others by their narrow segments with ruffled margins (versus wider segments with straight margins), and are here recognized as a separate species, L. tenuisecta . Quantitatively L. tenuisecta differs from L. hexasepala in several variables, notably its exceptionally long ligules (mean length 32.9 cm versus 10.4 cm) and longer middle segments (mean length 31.0 cm versus 20.0 cm).

Figures

FIGURE 17. Distribution maps of L. nuichuaensis, L. poilanei, L. tenuisecta, and L. verrucosa.

FIGURE 18. Type of L. tenuisecta (Henderson et al. 3707).