| Salviniales, the water ferns | |
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| Marsilea villosa | |
Scientific classification  | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Division: | Polypodiophyta |
| Class: | Polypodiopsida |
| Subclass: | Polypodiidae |
| Order: | Salviniales Link |
| Families | |
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| Synonyms | |
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The order Salviniales (formerly known as the Hydropteridales and including the former Marsileales) is an order of ferns in the class Polypodiopsida. [1]
Salviniales are all aquatic and differ from all other ferns in being heterosporous, meaning that they produce two different types of spore (megaspores and microspores) that develop into two different types of gametophyte (female and male gametophytes, respectively), and in that their gametophytes are endosporic, meaning that they never grow outside the spore wall and cannot become larger than the spores that produced them. The megasporangia each produce a single megaspore. [1] In being heterosporus with endosporic gametophytes they are more similar to seed plants than to other ferns.
The fertile and sterile leaves are dimorphic, taking on a different shape, and leaves bear anastomosing veins. Aerenchyma is frequently present in roots, shoots, and petioles (leaf stalks). [1]
The ferns of this order vary radically in form and do not look particularly fern-like. Species of the family Salviniaceae are natant (floating), while those of the family Marsileaceae are rooted. However, the natant species may temporarily grow on wet mud during times of low water, and the Marsileaceae may grow as emergent species, depending on species and location.
The group has also the smallest known genomes of all ferns. One genus, Azolla , is amongst the fastest growing plants on earth and caused a cooling of the climate in the Azolla event about 50 million years ago. [2]
There is a well-known fossil member of the Marsileales, Hydropteris (incertae sedis).
In the molecular phylogenetic classification of Smith et al. (2006), the Salviniales were placed in the leptosporangiate ferns, class Polypodiopsida. Two families, Marsileaceae and Salviniaceae, were recognized. [1] The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009) [3] which placed all land plants in Equisetopsida, [4] reclassified Smith's Polypodiopsida as subclass Polypodiidae and placed the Salviniales there. The circumscription of the order and its families was not changed, [3] and that circumscription and placement in Polypodiidae has subsequently been followed in the classifications of Christenhusz and Chase (2014) [5] and PPG I (2016). [6]
The likely phylogenic relationships between the two families and five genera of the Salviniales are shown in the following diagram. [7] [8]
| Salviniales |
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The ferns are a group of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissues that conduct water and nutrients and in having life cycles in which the branched sporophyte is the dominant phase.
Osmundaceae is a family of ferns containing four to six extant genera and 18–25 known species. It is the only living family of the order Osmundales in the class Polypodiopsida (ferns) or in some classifications the only order in the class Osmundopsida. This is an ancient and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Claytosmunda, Osmunda, Osmundastrum, and Plensium. In these genera the sporangia are borne naked on non-laminar pinnules, while Todea and Leptopteris bear sporangia naked on laminar pinnules. Ferns in this family are larger than most other ferns.
Ophioglossaceae, the adder's-tongue family, is a small family of ferns. In the Pteridophyte Phylogeny Group classification of 2016, it is the only family in the order Ophioglossales, which together with the Psilotales is placed in the subclass Ophioglossidae. The Ophioglossidae are one of the groups traditionally known as eusporangiate ferns. Members of the family differ from other ferns in a number of ways. Many have only a single fleshy leaf at a time. Their gametophytes are subterranean and rely on fungi for energy.
Schizaeales is an order of ferns.
Osmunda is a genus of primarily temperate-zone ferns of family Osmundaceae. Five to ten species have been listed for this genus.
Equisetales is an order of subclass Equisetidae with only one living family, Equisetaceae, containing the genus Equisetum (horsetails).
Gleicheniales is an order of ferns in the subclass Polypodiidae. The Gleicheniales have records potentially as early as the Carboniferous, but the oldest unambiguous records date to the Permian.
The Dryopteridaceae are a family of leptosporangiate ferns in the order Polypodiales. They are known colloquially as the wood ferns. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), the family is placed in the suborder Polypodiineae. Alternatively, it may be treated as the subfamily Dryopteridoideae of a very broadly defined family Polypodiaceae sensu lato.
The order Cyatheales, which includes most tree ferns, is a taxonomic order of the fern class, Polypodiopsida. No clear morphological features characterize all of the Cyatheales, but DNA sequence data indicate the order is monophyletic. Some species in the Cyatheales have tree-like growth forms from a vertical rhizome, others have shorter or horizontal expanding rhizomes.
Salviniaceae, is a family of heterosporous ferns in the order Salviniales. The Salviniaceae contain the two genera Azolla and Salvinia, with about 20 known species in total. The oldest records of the family date to the Late Cretaceous. Azolla was previously placed in its own family, Azollaceae, but research has shown Azolla and Salvinia to be sister genera with the likely phylogenic relationship shown in the following diagram.
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.
A pteridophyte is a vascular plant that disperses spores. Because pteridophytes produce neither flowers nor seeds, they are sometimes referred to as "cryptogams", meaning that their means of reproduction is hidden.
Psilotaceae is a family of ferns consisting of two genera, Psilotum and Tmesipteris with about a dozen species. It is the only family in the order Psilotales.
The Hymenophyllaceae, the filmy ferns and bristle ferns, are a family of two to nine genera and about 650 known species of ferns, with a subcosmopolitan distribution, but generally restricted to very damp places or to locations where they are wetted by spray from waterfalls or springs. A recent fossil find shows that ferns of Hymenophyllaceae have existed since at least the Upper Triassic.
The Polypodiidae, commonly called leptosporangiate ferns, formerly Leptosporangiatae, are one of four subclasses of ferns, the largest of these being the largest group of living ferns, including some 11,000 species worldwide. The group has also been treated as the class Pteridopsida or Polypodiopsida, although other classifications assign them a different rank. Older names for the group include Filicidae and Filicales, although at least the "water ferns" were then treated separately.
Pteris platyzomopsis, synonym Platyzoma microphyllum, is a fern in the family Pteridaceae. When placed in the genus Platyzoma, it was the only species; the genus was sometimes placed in its own family, Platyzomaceae. The species is native to northern Australia, occurring in the Kimberley region of Western Australia, in the Northern Territory and Queensland, and in northern New South Wales, where it is considered endangered. Vernacular names include braid fern.
The Dipteridaceae is a family of ferns in the order Gleicheniales of the class Polypodiopsida. They are commonly known as umbrella ferns and contain two genera, Cheiropleuria and Dipteris, with a total of nine species confined to Asia, New Guinea and northern Australia While currently a small family, they were much more abundant in the Mesozoic era, with the oldest fossils being known from the Middle Triassic of Italy, Australia and Argentina. Seven fossil genera are recognised, including Hausmannia, Clathropteris, Dictyophyllum, Thaumatopteris, Camptopteris, and Polyphacelus.
Hemidictyum is a genus of ferns with a single species, Hemidictyum marginatum, commonly known as the marginated half net fern. In the Pteridophyte Phylogeny Group classification of 2016, it is the only genus in the family Hemidictyaceae. Alternatively, the family, along with Aspleniaceae sensu stricto, may be placed in a much more broadly defined family Aspleniaceae as the subfamily Asplenioideae.
Ophioglossidae is one of the four subclasses of Polypodiopsida (ferns). This subclass consists of the ferns commonly known as whisk ferns, grape ferns, adder's-tongues and moonworts. It is equivalent to the class Psilotopsida in previous treatments, including Smith et al. (2006). The subclass contains two orders, Psilotales and Ophioglossales, whose relationship was only confirmed by molecular phylogenetic studies.
| Authority control databases: National |
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