Thelypteridaceae Pic.Serm.

Terrestrial (NZ) or rarely epiphytic (not NZ) ferns. Rhizomes short- to long-creeping, erect or forming a short arborescent trunk, scaly. Fronds monomorphic or rarely dimorphic, not articulated to rhizome. Laminae undivided (not NZ) or 1-pinnate to 3-pinnate-pinnatifid (NZ), catadromous, herbaceous or coriaceous, usually hairy, sometimes bearing glands, rarely also scaly, often with aerophores in two lines on stipe and rachis and on abaxial surfaces at bases of pinnae. Veins free (NZ), or with one or more basal veins from adjacent pinna lobes uniting below the sinus (NZ), or rarely reticulate (not NZ). Sori round (NZ) or slightly elongate (not NZ), superficial, borne on abaxial surface away from margins; paraphyses usually absent or rarely present; indusia reniform, irregularly shaped or absent; sporangial maturation mixed.  Sporangia with vertical annulus, usually 64 spores per sporangium. Homosporous; spores monolete (NZ) or rarely trilete (not NZ), lacking chlorophyll; perispores reticulate, winged, echinate or tuberculate.

A family of 5–25 genera depending on authority, and almost 1000 species.

Taxonomic classification of the family remains uncertain with many different treatments having been proposed. At one extreme, Christenhusz & Chase (2014) suggest that the Thelypteridaceae should be subsumed within a greatly expanded Aspleniaceae. However, that would create a very large family that is difficult to define morphologically, and the concept is not accepted here. Most recent authorities, including Smith et al. (2006), recognise Thelypteridaceae as a clearly defined, monophyletic family, but subdivision of the family is more contentious. Smith et al. (2006) recognise only Cyclosorus, Macrothelypteris, Phegopteris, Pseudophegopteris and Thelypteris, which Christenhusz & Chase (2014) would reduce further to just three genera, whereas Holttum (1971, 1977, 1982) grouped the Old World species into 25 genera. Holttum’s treatment has been criticised for needing combinations of characters to define genera, and because generic boundaries are blurred by possible hybridisation and transitional species (Smith 1990). Smith (1971) and Smith et al. (2006) included Christella within a more broadly circumscribed Cyclosorus. Molecular evidence is still preliminary and not yet conclusive, especially with respect to the clade that includes Christella, Cyclosorus and Pneumatopteris (Smith & Cranfill 2002; He & Zhang 2012). The most recent work suggests that Christella is polyphyletic, with most Paleotropical species, including C. dentata, not congeneric with Neotropical species (Almeida et al. 2016). Until there is greater clarity in the circumscription of these genera, we follow Holttum’s long-standing treatment of the family in the Pacific and Australasia (Holttum 1977) to provide consistency and comparability with listings for Australia (Bostock 1998), Fiji (Brownsey & Perrie 2011) and the south-west Pacific (Nakamura 2008).

On the basis of Holttum’s classification, the family is represented in New Zealand by five indigenous genera – Christella, Cyclosorus, Macrothelypteris, Pneumatopteris and Thelypteris. In stark contrast to the diversity in Australia and the Pacific, each of these genera is monotypic in New Zealand, and the five representatives are easily distinguished. Previously, they were all included in a broadly construed Thelypteris by Allan (1961).

The Thelypteridaceae comprise mostly terrestrial ferns with undivided to almost 4-pinnate fronds, which bear hairs and sometimes also glands and scales. Characteristically the stipes, rachises and pinna bases have aerophores, and the veins are mostly free, except that the basal veins of the pinna lobes often unite below the sinus. The sori are usually round, away from the margin, and either exindusiate or protected by reniform indusia. The sporangia have a vertical annulus, and almost always produce monolete spores.