Gleicheniales
| Gleicheniales | |
|---|---|
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|
| Dipteris conjugata of the Dipteridaceae | |
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta (but see text) |
| Class: | Polypodiopsida / Pteridopsida (disputed) |
| Order: |
Gleicheniales (but see text) A.B.Frank in Leunis |
| Families | |
| Synonyms | |
|
Gleicheniatae |
|
Dipteridaceae
Gleicheniaceae
Matoniaceae
Gleicheniatae
Gleicheniopsida
(but see text)
The ferns of the order Gleicheniales are – like all ferns and the related horsetails – sometimes placed in an infradivision Monilophytes of subdivision Euphyllophytina, 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 Gleicheniales showed up in the fossil record at least as early as the Cretaceous.
These ferns are characterized by root steles having 3–5 protoxylem poles and antheridia with 6–12 narrow, twisted or curved cells in their walls. Otherwise, their habitus is highly diverse, including plants with the typical fern fronds, others whose leaves resemble those of palm trees, and yet others again which have undivided leaves. They are tropical ferns, most diverse in Asia and the Pacific region.
In the molecular phylogenetic classification of Smith et al. in 2006, the Gleicheniales were placed in class Polypodiopsida (the leptosporangiate ferns). Three families, Dipteridaceae, Gleicheniaceae, and Matoniaceae were recognized. The linear sequence of Christenhusz et al. (2011), intended for compatibility with the classification of Chase and Reveal (2009) which placed all land plants in Equisetopsida, reclassified Smith's Polypodiopsida as subclass Polypodiidae and placed the Gleicheniales there. The circumscription of the order and its families was not changed, and that circumscription and placement in Polypodiidae has subsequently been followed in the classifications of Christenhusz and Chase (2014) and PPG I (2016).
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