Plants terrestrial or on rocks. Rhizomes stout, dictyostele radially symmetrical, branched or not, erect, ascending, or long creeping, with scales at apices; scales basiflexed, lanceolate or nearly ovate, brown, thick, luminae elongate, usually with grayish white short setae on dorsal side or ciliate along margins. Fronds clustered, approximate, or remote; stipes slender, stramineous, not articulate, with 2 crescent-shaped vascular bundles at base, usually scaly at bases, distally ± with grayish white unicellular acicular hairs, rarely with multicellular long hairs or stellate hairs. Fronds monomorphic, rarely subdimorphic, oblong-lanceolate or oblanceolate, sometimes ovate or ovate-triangular, usually pinnate-pinnatifid, sometimes 3- or 4-pinnate-pinnatifid, rarely 1-pinnate; pinnae symmetrical at bases; costae grooved adaxially but grooves not confluent with rachial grooves, or raised and with dense grayish acicular hairs, with expanded tuberculate aerophores at bases of pinnae. Laminae herbaceous or papery, sometimes somewhat leathery, green or dark brown-green when dry, both sides (particularly rachises, costae, and main veins adaxially) with grayish white unicellular acicular hairs, rarely glabrous, usually with orange or reddish orange, stalked or sessile spherical or club-shaped glands, occasionally small scaly along rachises and costae abaxially. Sori orbicular, oblong, or shortly linear, dorsifixed on veins, indusiate or exindusiate; indusia orbicular-reniform, fixed by deep notch, most ± hairy, persistent or hidden in sori, caducous, or not concentrated into sori but scattered along reticulate veins and exindusiate. Sporangia long stalked, usually with hairs or glandular hairs below annuli and at distal end of sporangial stalks. Spores bilateral, rarely tetrahedral, tuberculate, echinate, granular, or usually with a winged perispore. Prothalli green, cordate or narrowly cordate, usually with broad wings, symmetrical, usually with hairs or glands. x = 27-36 (lacking 28).

The family* is very natural and is distinguished from others by having grayish white unicellular acicular hairs and pubescence throughout the plant. However, there are many different viewpoints about generic circumscription in the family. Ching recognized 18 genera (including Hypodematium) in his 1963 treatment (Acta Phytotax. Sin. 8: 289-335); soon afterward, in 1978 (Ching, Acta Phytotax. Sin. 16(3): 12-13), the number of recognized genera in China grew to 20 (Hypodematium was removed and placed in its own family). In 1971, Holttum subdivided this family in the Paleotropics into 23 genera (Blumea 19(1): 17-52). In 1977, Pichi Sermolli, mainly following Holttum, circumscribed other genera for a total of 32 genera (Webbia 3(2): 213-512). In 1990, A. R. Smith divided the family into five genera (in Kramer & Green, Fam. Gen. Vasc. Pl. 1: 263-272), i.e., Thelypteris (including five subgenera), Phegopteris, Pseudophegopteris, Macrothelypteris, and Cyclosorus (including 20 subgenera). Of the many systems, those of Holttum and Pichi Sermolli divide the family most finely, with the greatest number of genera. Holttum (loc. cit.) segregated the following genera from Cyclosorus s.l.: Amphineuron, Christella, Pneumatopteris, and Sphaerostephanos. Recognition of these genera was based on several characters, including whether the proximal pinnae were shortened or not, and whether the sporangia and sporangial stalks bore hairs or glandular hairs. Holttum (loc. cit.) also segregated several genera (e.g., Parathelypteris and Coryphopteris) from the classical Thelypteris s.l., the free-veined thelypteroids, by characters that included rhizome habit, laminar glands, and chromosome base number. Smith (loc. cit.: 265) noted: "Although many of Holttum’s genera seem natural (i.e., monophyletic), a combination of characters must be used to circumscribe them. Some of the characters concern minute glands and hairs and require 30 × magnification or greater for observation. Others require that complete specimens be at hand (including lower part of blade and stem). Even then, identification to genus may be difficult, as generic lines are not always sharp." The question of generic delimitation within the family needs further study, but for now we adopt Ching’s system (1978), modified from Ching (1963).**

*In 1940, Ching established many new families (Sunyatsenia 5(4): 237), including Thelypteridaceae with 12 genera, but the names of these new families are nomina nuda and were not therefore validly published (Melbourne Code, Art. 38.1(a)). Only in 1970 were these families formally published by Pichi Sermolli.

**(1) Holttum set up the genus Amphineuron with mixed characters in 1971, which was also adopted by Ching in 1978. Among the 12 recognized species in the genus, three occur in China: the type species A. opulentum, which is similar to Cyclosorus in venation and lemon-yellow glands; A. immersum, which is similar to Parathelypteris species in venation; and A. tonkinensis, which has already been removed to a new genus, Mesopteris. As Holttum himself considered Amphineuron to be a provisional treatment, this genus is not adopted here.

(2) Trichoneuron Ching (Acta Phytotax. Sin. 10: 118, pl. 22. 1967) was based on a single gathering, and the collection locality was unknown. Later, this species was rediscovered by Prof. W. M. Chu in Pingbian, SE Yunnan. According to Prof. Chu’s study, it belongs to the genus Lastreopsis (Dryopteridaceae). It is, therefore, not included here.

Using only venation, the family may be divided into 3 tribes: 1. Tribe Thelypterideae Ching: Veins free; with two subtypes: (1) all veinlets reaching margins or nearly reaching margins above sinuses between segments, with the bottom of sinuses not cartilaginous (e.g., Parathelypteris); (2) proximal pair of veinlets from adjacent segments reaching cartilaginous sinuses but not united; or acroscopic veinlet of basal pair of veinlets reaching cartilaginous sinus, basiscopic veinlet reaching margin above sinus (e.g., Pseudocyclosorus and Mesopteris); 2. Tribe Goniopterideae Ching: Veins partly combined; at least proximal pair of veinlets from adjacent segments united to form triangular areoles and this vein union producing a long or short excurrent veinlet; additional areoles may be produced in the same row, by subsequent vein unions of veinlets; excurrent veinlets may connect with more distal vein unions, or with a translucent line leading to a sinus, thus forming oblique rhomboid areoles (goniopteroid venation) (e.g., Cyclosorus, Ampelopteris), or squarish areoles (meniscioid venation) (e.g., Pronephrium, the areoles without included veinlets; 3. Tribe Dictyoclineae Ching: Veinlets between lateral veins all combined into irregular squarish or pentagonal areoles and each areole sometimes with simple or forked included veinlets.

The following taxon is excluded from the present treatment, pending further research: Thelypteris calvata Ching (Bull. Fan Mem. Inst. Biol. Bot. ser. 2, 1: 313. 1949), described from Guangdong.

Shing Kunghsia, Chiu Peishi, Yao Guanhu & Lin Youxin. 1999. Thelypteridaceae. In: Shing Kunghsia, ed., Fl. Reipubl. Popularis Sin. 4(1): 15-317, 319-353.

About 20 genera and ca. 1,000 species, more at lower elevations, very few tropical species above 4500 m: widespread in all tropical and subtropical zones of the world, less common in temperate zone, particularly more common in Asia; 18 genera (one endemic) and 199 species (102 endemic) in China.

(Authors: Lin Youxing (林尤兴), Li Zhongyang (李中阳); Kunio Iwatsuki, Alan R. Smith)