12. Pteris deltodon Baker, J. Bot. 26: 226. 1888.
岩凤尾蕨 yan feng wei jue
Pteris nana Christ; P. trifoliata Christ (1899), not Fée (1857).
Plants 15-25 cm tall. Rhizome erect, short, ca. 1 cm in diam., apex with black-brown scales. Fronds clustered, submonomorphic; stipe brown at base, upper part straw-colored, slightly lustrous, 10-20 cm × 1-2 mm; sterile lamina similar to fertile lamina in shape but shorter and wider, terminal pinnae oblong-lanceolate, lateral pinnae ovate, margins serrate except at base; fertile lamina pinnate, ovate to triangular-ovate, 10-20 × 4-7 cm; pinnae 3-5; terminal pinna broadly lanceolate, 5-8 × 1.2-2 cm wide, sessile or shortly stalked, base broadly cuneate, sterile margins triangular-serrate toward apex, remainder entire, apex acuminate; lateral pinnae smaller, opposite, decumbent, falcate, sessile, base obtuse and oblique, apex mucronate. Lamina light brown, papery when dried, glabrous on both surfaces; costae straw-colored, abaxially convex; veins conspicuous, simple or forked. n = 53, 2n = 106.
On dark and slightly dry limestone, common in limestone soils in SW China; 300-2500 m. SW Guangxi (Longsheng), Guizhou (Anlong, Duyun, Pingtang), Sichuan, Taiwan, Yunnan (Guangnan, Maguan, Pingbian), Zhejiang [Japan (Ryukyu Islands), Laos, Vietnam].
Pteris sanduensis X. Y. Wang & P. S. Wang (Pterid. Fl. Guizhou, 598-599. 2001) was compared in the protologue to P. deltodon and P. crassiuscula where it was separated by the dimorphic fronds, the sterile fronds with terminal pinna 8-11 × 7-8 cm.