The forked ferns are the family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Gleicheniaceae. They are sometimes – like all fern

Fern

A fern is any one of a group of about 12,000 species of plants belonging to the botanical group known as Pteridophyta. Unlike mosses, they have xylem and phloem . They have stems, leaves, and roots like other vascular plants...

s and the related horsetail

Horsetail

Equisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...

s – placed in an infradivision Monilophytes of subdivision Euphyllophytina

Euphyllophytina

Euphyllophytina, the euphyllophytes, is a taxon – sometimes unranked, sometimes placed at the informal rank of subdivision – within the tracheophytes. It is sister to subdivision Lycopodiophyta. Euphyllophytina contains the two groups Spermatophytes and Monilophytes , as well as a...

, allowing for more precise phylogenetic arrangement of the tracheophytes. More conventionally, the name Pteridophyta, ranked as a division, is used in lieu of the Monilophytes. The formerly independent families Dicranopteridaceae and Stromatopteridaceae are nowadays generally included in the Gleicheniaceae, whereas the Dipteridaceae and Matoniaceae, though closely related, are considered spearate families by most authors.

These tropical ferns are the most widespread living lineage of Gleicheniales. Their rhizome

Rhizome

In botany and dendrology, a rhizome is a characteristically horizontal stem of a plant that is usually found underground, often sending out roots and shoots from its nodes...

s have a "vitalized" protostele or in some taxa a solenostele. The leaves are indeterminate, with pseudodichotomously

Dichotomy

A dichotomy is any splitting of a whole into exactly two non-overlapping parts, meaning it is a procedure in which a whole is divided into two parts...

 forked leaves except in Stromatopteris, and free veins. The sori

Sorus

A sorus is a cluster of sporangia .In fungi and lichens, the sorus is surrounded by an external layer. In some red algae it may take the form of a depression into the thallus....

 are abaxial but not marginal and carry 5-15 exindusiate round sporangia each. These have a transverse-oblique annulus and contain 128 to 800 bilateral or globose-tetrahedral spore

Spore

In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoa. According to scientist Dr...

s. The sori and sporangia mature at the same time, and the spores grow into surface-dwelling green prothallium

Prothallium

A prothallium, or prothallus is usually the gametophyte stage in the life of a fern or other pteridophyte, i.e. a spore-bearing plant with vascular tissue...

s beset with club-shaped hairs.

Systematics

There is some dispute about ranking these ferns. They are typically placed in the order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 Gleicheniales. This is alternatively be considered a subclass Gleicheniatae or class

Class (biology)

In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...

 Gleichenopsida, so that a distinct taxon can be established for the leptosporangiate fern

Leptosporangiate fern

Leptosporangiate ferns are the largest group of living ferns. They are often considered to be the class Pteridopsida or Polypodiopsida, although other classifications assign them a different rank...

s. In this case, the Gleicheniaceae are upranked to an order and receive the name Gleicheniales. Irrespective of their modern taxonomic treatment, the Gleicheniaceae were formerly included in the order Polypodiales

Polypodiales

The order Polypodiales encompasses the major lineages of polypod ferns, which comprise more than 80% of today's fern species. They are found in many parts of the world including tropical, semitropical and temperate areas...

. But the ferns in the loose sense are much too diverse a group to be shoehorned into one taxon

Taxon

|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...

 at such a low rank.

The Triassic

Triassic

The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 Antarctipteris and Gleichenipteris are sometimes ascribed to the Gleicheniaceae, but are probably better considered Gleicheniales incertae sedis

Incertae sedis

, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...

. The two living subfamilies contain six genera

Genera

Genera is a commercial operating system and development environment for Lisp machines developed by Symbolics. It is essentially a fork of an earlier operating system originating on the MIT AI Lab's Lisp machines which Symbolics had used in common with LMI and Texas Instruments...

:

Subfamily Gleichenioideae

• Dicranopteris
• Diplopterygium
• Gleichenella
• Gleichenia
  Gleichenia
  Gleichenia is a genus of ferns.Species include:* Gleichenia abscida Rodway* Gleichenia alpina R.Br.* Gleichenia dicarpa R.Br. – Pouched Coral Fern, Tangle Fern* Gleichenia mendellii S.B.Andrews...
  
  
• Sticherus
  Sticherus
  Sticherus is a genus of about 80 types of fern.In Australia they are commonly referred to as Shield Ferns.The fronds are branched at least once with each pair of branches spreading out, forming an umbrella like layer of foliage...
  
  

Subfamily Stromatopteridaeae

• Stromatopteris