Ophioglossidae is one of the four

subclasses Subclass may refer to: * Subclass (taxonomy), a taxonomic rank below "class" * Subclass (computer science) * Subclass (set theory) In set theory and its applications throughout mathematics, a subclass is a class contained in some other class in ...

Polypodiopsida A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...

(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 Psilotaceae is a family of ferns (class Polypodiopsida) consisting of two genera, '' Psilotum'' and ''Tmesipteris'' with about a dozen species. It is the only family in the order Psilotales. Description Once thought to be descendants of early v ...

and

Ophioglossales Ophioglossaceae, the adder's-tongue family, is a small family of ferns. In the Pteridophyte Phylogeny Group classification of 2016 (PPG I), it is the only family in the order Ophioglossales, which together with the Psilotales is placed in the sub ...

, whose relationship was only confirmed by

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

studies.

Taxonomy

Smith et al. (2006) carried out the first higher-level pteridophyte classification published in the

era, and considered the ferns (monilophytes), with four classes. They placed the whisk ferns and related taxa in the class Psilotopsida, with two

orders Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

Mark W. Chase Mark Wayne Chase (born 1951) is a US-born British botanist. He is noted for work in plant classification and evolution, and one of the instigators of the Angiosperm Phylogeny Group-classification for flowering plants which is partly based on DNA ...

and James L. Reveal (2009) classified them as two separate subclasses, Psilotidae and Ophioglossidae, corresponding to those orders within a much broader grouping, the class Equisetopsida ''sensu lato''. Christenhusz ''et al.'', 2011, included both the

and

orders in the Ophioglossidae subclass. This was continued by both

Christenhusz Dr Maarten Joost Maria Christenhusz (born 27 April 1976) is a Dutch botanist, natural historian and photographer. Career He was born in Enschede, the Netherlands, received his undergraduate and master's degrees from Utrecht University in Bi ...

and

Chase Chase or CHASE may refer to: Businesses * Chase Bank, a national bank based in New York City, New York * Chase Aircraft (1943–1954), a defunct American aircraft manufacturing company * Chase Coaches, a defunct bus operator in England * Chase C ...

(2014) and by the Pteridophyte Phylogeny Group (2016). Under the latter the subclass is one of four subclasses of

(ferns) and contains two orders, two families, 12 genera, and an estimated 129 species. The relationships between the two orders, Psilotales and Ophioglossales, has long been unclear and was only confirmed by molecular systematic studies. Psilotales have rhizomes instead of real roots, and the roots of Ophioglossales lack both branching and root hairs. The gametophytes of both orders are heterotrophic and often subterranean, obtaining nutrients from mycorrhiza instead of light. Photosynthesis happens exclusively in the

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote p ...

.Plant Systematics
/ref> The following cladogram shows a likely phylogenic relationship between subclass Ophioglossidae and the other Polypodiopsida subclasses. The first three small subclasses are sometimes informally referred to as

eusporangiate fern Eusporangiate ferns are vascular spore plants, whose sporangia arise from several epidermal cells and not from a single cell as in leptosporangiate ferns. Typically these ferns have reduced root systems and sporangia that produce large amounts o ...

s, in contrast to the largest subclass, Polypodiidae or

leptosporangiate fern The Polypodiidae, commonly called leptosporangiate ferns, formerly Leptosporangiatae, are one of four subclasses of ferns, and the largest of these, being the largest group of living ferns, including some 11,000 species worldwide. The group has ...

s. The two orders,

and

are sister groups to each other.

References

Bibliography

* * * * * * * Plant subclasses {{fern-stub