Lanonia acaulis (Henderson, Ninh Khac Ban & Nguyễn Quốc Dựng) Henderson & Bacon (2011: 888)

Henderson, Andrew & D ựng, Nguy ễn Qu ốc, 2022, A revision of Lanonia (Arecaceae, Coryphoideae, Livistoninae), Phytotaxa 532 (3), pp. 209-245 : 221-222

1. Lanonia acaulis (Henderson, Ninh Khac Ban & Nguyễn Quốc Dựng) Henderson & Bacon (2011: 888) .

Licuala acaulis Henderson , Ninh Khac Ban & Nguyễn Qu ốc Dựng (2008: 142). Type:— VIETNAM. Da Nang City , Hoa Vang District , Ba Na-Nui Chua Nature Reserve , road to summit, 16°00’N 108°01’E, ca. 500 m, 19 April 2007, A. Henderson, Nguyễn Qu ốc Dựng, Nguyen Canh & Le Van Bo 3302 (holotype HN!, isotype NY!) .

Stems 0.4 m long, diameter not recorded, solitary. Leaves number per stem not recorded; ligules length not recorded, soon disintegrating into fibers; sheaths and proximalmost part of petioles with scattered, brown scales; petioles length not recorded, 0.8(0.7–0.9) cm wide at the apex; petiole thorns usually poorly developed, brown or black, more or less regularly arranged on proximalmost part of petiole; hastulas raised, triangular, infolded; leaf blades 108.0 cm wide; costas 5.8(3.5–8.0) cm long, triangular, with a pulvinus at the apex abaxially, with the numerous segments free almost to the base; segments 27(22–32) per leaf, mottled, with minute, reddish-brown scales abaxially, with (on dried specimens) straight margins; middle segments 59.8(59.5–60.0) cm long, 5.0 cm wide at the apex; apices of middle segments with adaxial splits not much deeper than abaxial ones. Inflorescences length not recorded; prophylls and peduncles length not recorded; rachis bracts flattened, splitting apically and laterally, usually densely brown tomentose; rachillae thick and ribbed, densely covered with wooly, much branched, reddish-brown hairs; staminate rachises absent; staminate partial inflorescences 1, branched to 3 orders; staminate rachillae number not recorded, 26.5 cm long, 2.7 mm diameter; staminate flowers 5.5 mm long; sepals not pedicellate at the base, not densely hairy; petals with a narrowed apex, solid internally; stamens with equal filaments and longer, rectangular anthers; filaments elongate; pistillodes undivided; pistillate rachises absent or 8.0 cm long; pistillate partial inflorescences 1–2, branched to 3 orders; pistillate rachillae on proximalmost partial inflorescence 12(10–16), 13.0(12.5–13.5) cm long, 2.4(1.8– 3.2) mm diameter; pistillate flowers 4.8(4.5–5.0) mm long, with elongate styles; fruits size and shape not recorded, reddish, with uneven, ridged surfaces; seeds not recorded.

Distribution and habitat:— Central Vietnam in Da Nang City, known only from Ba Na-Nui Chua Nature Reserve, on steep slopes in lowland rainforest at 600(500–800) m elevation ( Fig. 8 ).

Taxonomic notes:— Specimens determined as preliminary species Lanonia acaulis were polymorphic for hastulas. One specimen (Henderson 3551) from Sao La Nature Reserve was included in L. acaulis by Henderson & Nguyễn Quốc Dựng (2019) and in L. dasyantha by Henderson & Bacon (2011). However, the specimen has a rounded hastula and may not to be either species, and is here excluded and remains unidentified. With this specimen excluded, other specimens share a unique combination of qualitative variable states and are therefore recognized as a phylogenetic species.

Lanonia acaulis is notable for its short stems, mottled leaves, thick and ribbed rachillae, long staminate and pistillate flowers, staminate petals with a narrowed apex, and uneven, ridged fruit surfaces. In these it resembles L. dasyantha .

Figures

FIGURE 8. Distribution maps of L. acaulis, L. batoensis, L. calciphila, and L. centralis.