Evolution and Classification
Ferns first appear in the fossil record in the early Carboniferous epoch. By the Triassic the first evidence of ferns related to several modern families appears. The great fern radiation occurred in the late Cretaceous, where many modern families of ferns first appear.
Ferns have traditionally been grouped in the class Filices, but some modern classifications assign them their own division in the plant kingdom, which may be known as Pteridophyta.
Two related groups of plants, commonly known as ferns, are more distantly related to the main group of ferns: the whisk ferns (Psilophyta) and the adders-tongues, moonworts and grape-ferns (Ophioglossophyta). The Ophioglossophytes were formerly considered "true" ferns, and were grouped in the family Ophioglossaceae, but were subsequently found to be more distantly related. Some classification systems include the Psilopytes and Ophioglossophytes in division Pteridophyta, while others assign them separate divisions. Modern phylogeny indicates that the Ophioglossophytes, Psilopytes, and true ferns together constitute a monophyletic group, descended from a common ancestor.
The "true" ferns may be subdivided into four main groups, or classes (or orders if the ferns are considered as a class):
The last group includes most plants familiarly known as ferns. The Marattiopsida are a primitive group of tropical ferns with a large, fleshy rhizome, and are now thought to be a sister taxon to the main group of ferns, the leptosporangiate ferns, which include the other three groups listed above. Modern research indicates that the Osmundopsida diverged first from the common ancestor of the leptosporangiate ferns, followed by the Gleichenopsida.
A more complete classification scheme follows:
- Division: Pteridophyta
- Class: Marattiopsida
- Class: Osmundopsida
- Order: Osmundales (the flowering ferns)
- Class: Gleicheniopsida
- Subclass: Gleicheniatae
- Order: Gleicheniales (the forked ferns)
- Order: Dipteridales
- Order: Matoniales
- Subclass: Hymenophyllatae
- Order: Hymenophyllales (the filmy ferns)
- Subclass: Hymenophyllopsitae
- Order: Hymenophyllopsidales
- Class: Pteridopsida
- Subclass: Schizaeatae
- [heterosporous ferns]
- Subclass: Cyatheatae
- Subclass: Pteriditae
- Order: Lindseales
- Order: Pteridales (including the brakes and maidenhair ferns)
- Order: Dennstaedtiales (the cup ferns)
- Order: Hypolepidales (including bracken)
- Subclass: Polypoditae
- Order: Aspleniales (the spleenworts)
- Order: Athyriales (including the lady ferns, ostrich fern, maiden ferns, etc.)
- Order: Dryopteridales (the wood ferns and sword ferns)
- Order: Davalliales (including the rabbits-foot ferns and Boston ferns)
- Order: Polypodiales (including the rock-cap ferns or Polypodies)
