
Thelypteridaceae

Thelypteridaceae is a family of about 900 species of ferns in the order Polypodiales. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), it is placed in the suborder Aspleniineae. Alternatively, the family may be submerged in a very broadly defined family Aspleniaceae as the subfamily Thelypteridoideae.
The ferns are terrestrial, with the exception of a few which are lithophytes (grow on rocks). The bulk of the species are tropical, although there are a number of temperate species.
These ferns typically have creeping rhizomes. The fronds are simply pinnate to pinnate-pinnatifid. There is either no frond dimorphism or only mild dimorphism, either open venation or very simple anastomosing. The sori are mostly reniform in shape and have indusia, except for the "Phegopteris" group.
Classification.
At one time, all thelypterioid ferns were included in the genus "Dryopteris" because of the sorus shape. However, there are a great many differences between the groups, and these plants are now segregated in their own family. Genetic evidence shows that the family is clearly monophyletic.
Phylogenetic relationships.
The following cladogram for the suborder Aspleniineae (as eupolypods II), based on Lehtonen (2011), and Rothfels & al. (2012), shows a likely phylogenetic relationship between the Thelypteridaceae and the other families of the clade.
Genera.
The family can be divided into two major clades, which the Pteridophyte Phylogeny Group classification of 2016 (PPG I) recognizes as two subfamilies, Phegopteridoideae and Thelypteroideae. Their division into genera has been described as "highly controversial and fluctuating". The family includes several complexes of species that are difficult to distinguish, and seem to represent a remarkable evolutionary radiation. Some researchers include the entire family Thelypteridaceae in the genus "Thelypteris"; others divide the family into as many as 30 genera. An intermediate position is to place the bulk in "Thelypteris" (which can then be divided into subgenera and sections corresponding to the genera of other authors) but to separate out "Phegopteris" and "Macrothelypteris". Another choice is to divide the family into a half a dozen or so genera.
The Pteridophyte Phylogeny Group classification of 2016 (PPG I) accepts 30 genera:
The extinct genus "Holttumopteris" from the Cenomanian aged Burmese amber has been suggested to have affinities with the family, but several important diagnostic characters are not preserved.