Etymology

Named after the district of Thailand (Phanom) in which the type was collected.

Family

Pteridaceae, subfamily Vittarioideae

Nomenclature

Adiantum phanomensis S.Linds. & D.J.Middleton, Harvard Pap. Bot. 8: 137. 2004. – Type: Thailand, Surat Thani, Amphoe Phanom, Khlong Phanom National Park, c.100 m alt., 11 Aoril 2003, Middleton et al. 2133 (holo BKF; iso A, BKF).

Description

Lithophytic on soft eroding limestone. Rhizome short, erect, covered with scales; scales narrow, black with a brown margin, 2–3 mm long, 0.1–0.2 mm wide. Stipe dark brown, 0.5–5.8 cm long, glabrous or with few scales near base. Laminae simply pinnate, 3–13 cm long, 1.4–4 cm wide, oblong in outline; rachis glabrous; pinnae 3–12 on each side of rachis, gradually becoming slightly smaller upwards; pinnae on stalks 2–8 mm long; pinnae flabellate, 6.5–20 by 5–11 mm, base narrow forming an angle of 40–80°, margins entire and straight, flat apex only weakly lobed with a narrow, inconspicuous sinus; thin, glabrous above, densely brown to grey pubescent beneath; veins dichotomous, slightly raised above (not visible beneath due to pubescence). Sori on flat apex of lobes, 2–4 reflexed soral flaps (false indusia), elongate , 2–4 mm long.

Distribution in Thailand

PENINSULAR: Surat Thani.

Wider Distribution

Endemic to Thailand. Known only from Klong Phanom and Khao Sok National Parks.

Ecology

On steep banks of soft eroding limestone.

Similar species

Adiantum gomphophyllum Baker

Proposed IUCN Conservation Assessment

Least Concern (LC). This species is geographically restricted but occurs in two well protected areas in Khao Sok and Khlong Phanom National Parks in Thailand.

Voucher specimens - Thailand

Middleton et al. 4322, Surat Thani, Khao Sok National Park (E); Middleton et al. 4359 & 5550, Surat Thani, Khlong Phanom National Park (E).