Family

Thelypteridaceae

Nomenclature

Cyclosorus thailandicus S.Linds., Thai For. Bull. (Bot.) 36: 47. 2008. – Type: Middleton et al. 1748, Phetchaburi, Kaeng krachan (holo BKF; iso A).

Description

Small terrestrial fern with delicate fronds. Rhizome short creeping or suberect with closely spaced fronds; scales pale brown, narrowly triangular, 3–4.5 x 0.5–0.8 mm, uniformly coloured, minutely pubescent, margins entire. Stipes purplish, 1–6 cm long, scaly at base only. Laminae decrescent at base, widest slightly above the middle, 34.5–37 x 9.5–12 cm; 11–14 pairs of lateral pinnae; terminal pinna largest, apex acuminate, 11–12.5 x 1.4–2.5 cm, incise 1/4–1/3 way towards costa; 4–5 pairs of basal pinnae, gradually reduced, butterfly-shaped, c. 1 x 1 cm; lateral pinnae sessile, c. 2 cm apart, oblong, base truncate, first acroscopic pinnule somewhat larger, apex acuminate, incised 1/4 way towards costule, 3.5–8.3 x 0.8–1.2 cm; rachis and costae pubescent above with acicular hairs, costae and lamina minutely pubescent all over beneath; veins 5–6 pairs, of which lowest pair anastomose, the second pair have the distal vein anastomosing with the intercostule vein, the proximal vein runs to sinus. Sori mostly very closely paired, confluent, in a single row in lower parts of pinnae, sometimes 2 or 3 in upper parts, situated where the first pair of veins anastomose below the sinus in lower parts, also on second or third veins in upper parts; indusium densely pubescent, reniform. Spores monolete & ellipsoidal, with short low ridges.

Distribution in Thailand

SOUTH-WESTERN: Phetchaburi.

Wider Distribution

 Endemic to Thailand. Only known from Kaeng Krachan National Park.

Ecology

Collected in primary evergreen forest in sandy-stony soil beside river in deep shade at 330 m altitude.

Proposed IUCN Conservation Assessment

Data Deficient (DD). The species is currently only known from the type specimen which was collected in a river bed, a habitat that could be subject to sudden and catastrophic change. However, it is unknown to what extent the species also occurs in the very extensive and protected surrounding forest.