Lanonia gialaiensis Henderson & Nguy

6. Lanonia gialaiensis Henderson & Nguy ễn Quốc Dựng (2017: 160). Type:— VIETNAM. Gia Lai province, Ho Chi Minh Highway, East Branch, 14˚33’ N 108 ˚26’ E, 1,250 m, 22 April 2017, A. Henderson & Nguyễn Qu ốc Dựng 4221 (holotype VFM!, isotype NY!).

Stems 1.0m long, diameter not recorded, clustered. Leaves number not recorded; ligules 2.5 cm long, soon disintegrating into fibers; sheaths and proximalmost part of petioles with dense, flat, black scales; petioles 26.8(18.0–35.5) cm long, 0.3 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 width not recorded; costas 1.8(1.6–2.0) cm long, triangular, with a pulvinus at the apex abaxially, with the few segments free almost to the base; segments 6(4–7) per leaf, not mottled, with minute, reddish-brown scales abaxially, with (on dried specimens) straight margins; middle segments 17.0(16.0–18.0) cm long, 3.8 cm wide at the apex; apices of middle segments with adaxial splits not much deeper than abaxial ones. Inflorescences 20.0 cm long; prophylls and peduncles not recorded; rachis bracts flattened, splitting apically and laterally, usually densely brown tomentose; rachillae not filiform nor thick and ribbed, densely covered with erect, branched, translucent hairs; staminate inflorescences not recorded; pistillate rachises absent; pistillate partial inflorescences 1, branched to 2 orders; pistillate rachillae on proximalmost partial inflorescence 5, 7.3 cm long, 1.6 mm diameter; pistillate flowers length not recorded, with short styles; fruits not recorded; seeds not recorded.

Distribution and habitat:— Southern Vietnam in Gia Lai province in montane rainforest at 1,250 m elevation (Fig. 9).

Taxonomic notes:— Specimens determined as preliminary species Lanonia gialaiensis share a unique combination of qualitative variable states and are therefore recognized as a phylogenetic species.

Lanonia gialaiensis is notable for its stout, reddish-brown petiole thorns. In these it resembles a group of similar and apparently related species (L. gialaiensis, L. hexasepala, L. honbaensis, L. manglaensis, L. montana, L. tenuisecta) from higher elevations in southern Vietnam.