The Pteroid frond family has undergone numerous changes in classification and it is still a work in progress.
It has been divided into groups, tribes or subfamilies with variations in the genera included.
The current subfamilies are Cryptogrammoidea, Parkerioideae, Pteridoideae, Cheilanthoideae and Vittarioideae.
Estimates of the number of genera range from 45 to 68 with 950 to 1375 species.
Adiantaceae and Vittariaceae can be seen as their original families, as synonyms for the new and inclusive Pteridaceae
or reduced to subfamilies in it.
The genera included should be noted to decide what a description actually refers to.
The defining feature of the family is the absence of a true indusium over the sori.
(Sori are collections of spore producing sporangia.)
A true indusium is a flap of epidermal tissue growing over a sorus.
A false indusium is formed by the edge of the frond folding back over the sorus.
Sometimes neither is present.
The ferns are mainly terrestrial or epiphytic with some growing on rocks and a few in swampy areas.
The rhizomes can be creeping or erect and with or without hairs or scales.
A few have simple fronds (leaves) but in most they are pinnate, bipinnate or more divided.
Prominent hairs or scales may be present or absent and the veins may anastomose or be free.
Typically the sori are around the edge of the leaf covered by a false indusium.
The fold may be continuous or there may be a separate fold, variously shaped over each sorus.
Sori may also lie along the veins without any indusium.