The Thelypteridaceae as a family includes those members formerly placed in the genus Thelypteris, sensu latu. In fact, the entire family was at one time only considered to be a section or two of the genus Dryopteris (or Aspidium), a group to which it is actually only remotely related.
This family includes several complexes of species that are difficult to distinguish, and seem to represent a remarkable evolutionary radiation.
Recent genetic evidence shows that the family is clearly monophyletic. The same genetic studies show that the traditional genus Phegopteris is, in fact, a clearly segregate group that diverges at the very base of the family tree. In fact, this particular clade also includes the genera Pseudophegopteris[?] and Macrothelypteris[?], which are here included in the larger genus Phegopteris. Similarly, Coryphopteris is included here in the genus Metathelypteris, Parathelypteris is included in Amauropelta, and a large group of genera are included in Cyclosorus.
This family typically has creeping rhizomes, simply pinnate to pinnate-pinnatifid fronds, either no frond dimorphism or only mild dimorphism, either open venation or very simple anastomosing, sori mostly reniform and indusiate, except for the Phegopteris group.
