Description from Flora of China
Rumohra hainanensis Ching, Sinensia 5: 44. 1934.
Rhizome shortly creeping, stiff, 2-3 cm in diam., apex densely scaly; scales reddish brown, linear-lanceolate, apex sometimes filiform, to 2 cm × 1.5 mm, spreading and soft. Fronds approximate, dimorphic, 30-60 cm. Sterile fronds 30-45 cm; stipe stramineous, 13-20 cm, ca. 2.5 mm in diam., base with scales similar to those on rhizome, scales sparser upward, appressed; lamina 2-pinnate, yellowish brown when dried, deltoid-lanceolate or lanceolate, 25-30 × 10-15 cm, subleathery, base rounded-cuneate, apex attenuate, rachis scaly as distal portion of stipe; pinnae 15-20 pairs, stalked, alternate or lower pairs opposite, spreading, lanceolate or deltoid-oblong, base rounded or broadly cuneate, apex acute or obtuse; pinnules 5-8 pairs per pinna, shortly stalked, oblong, to 2 × 0.8 cm, base acroscopically truncate and hardly auriculate, basiscopically cuneate, apex obtuse, margin serrate with mucronate teeth; axes of lamina, pinna, and pinnules with sparse minute brown filiform scales abaxially. Fertile fronds to 60 cm; stipe often 1/3 longer than lamina; lamina similar to that of sterile fronds in shape and dissection, but strongly contracted with much shorter and narrower pinnae. Sori small, terminal on veinlets, approximate, 4-8 pairs per ultimate segment, closer to midvein than margin; indusia dark brown, membranous, ciliate or irregularly denticulate on margin.
Arachniodes dimorphophyllum (Hayata) Ching (Acta Bot. Sin. 10: 257. 1962 ["dimorphyllum"]; Polystichum dimorphophyllum Hayata, J. Coll. Sci. Imp. Univ. Tokyo 30: 428. 1911; Rumohra dimorphophyllum (Hayata) H. Itô), the most closely related species to this fern, is reportedly from Taiwan. However, without available specimens, it is not included here and reserved for further verification.
● Shaded wet moss-covered rocks in dense or open forests, also in thickets or in crevices on arid cliffs by streams; 400-500 m. Hainan.