Lanonia batoensis Henderson & Nguyen Quoc Dung 2017, sp. nov.

Type:— VIETNAM. Quang Ngai: Ba To District, road from Ba To to Ba Cung, 14°44’N, 108°53’E, ca. 600 m, 18 July 2012, A. Henderson, Nguyen Quoc Dung & Le Van Tuan 3818 (holotype VFM!, isotype NY!).

It differs from other species in its inflorescences projecting above the leaves, tubular rachis bracts, and 10.0– 23.5 cm long, pendulous rachillae.

Stems solitary, 1.8 m tall, 3.0 cm diameter. Leaves 12; sheaths not recorded; ligules short, to 2 cm long; petioles 85.0 cm long, thorny along the margins for the ca. proximal one third; blades to 65.0 cm across, split into 19–20 approximately equally wide segments; costa 2.0 cm long; central segment split into 2 lobes, these 40.5–51.0 cm long, 1.3–1.4 cm wide at the apex; lateral segment not recorded; segments briefly indented at the apex. Inflorescences erect, projecting above the leaves, 115.0–130.0 cm long; staminate inflorescences branched to 3 orders; prophylls not recorded; peduncles not recorded; partial inflorescences 6, each subtended by a tubular rachis bract; rachillae to 23.5 cm long, minutely hairy; staminate flowers not seen; pistillate inflorescences branched to 2 orders; prophylls not recorded; peduncles with 4, narrow, tubular, glabrous peduncular bracts; partial inflorescence 1; rachillae 10.0–18.0 cm long, glabrous, pendulous; pistillate flowers not seen at anthesis, solitary; calyx 3-lobed above, each lobe splitting again as the fruits develop to give a 6-lobed calyx; corolla with 3 petals; fruits not recorded.

Distribution and habitat:—Central Vietnam in Quang Ngai province in lowland rainforest at 600 m elevation.

Taxonomic notes:— Lanonia batoensis appears most similar to a group of Lanonia species having numerous, more or less equally wide segments (L. acaulis, L. centralis, L. poilanei). It differs from these in its tubular (versus flattened) rachis bracts and longer, pendulous rachillae.

Additional specimen examined. VIETNAM. Quang Ngai: Ba To District, road from Ba To to Ba Cung, 14°44’N, 108°53’E, ca. 600 m, 18 July 2012, Henderson, Nguyen Quoc Dung & Le Van Tuan 3819 (NY, VFM).