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Polypodiopsida

(Class)

Overview

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The Pteridopsida is a class of in the Division Pteridophyta that includes all the leptosporangiate ferns. In the recent 2006 classification by Smith et al. the class is renamed Polypodiopsida. This recent reclassification of Monilophyte (ferns) is based on multiple molecular studies published since 1994 that have clarified some of the confusion of the placement and relations among fern families.1] Polypodiopsida is one of four classes of Monilophytes (an Infradivision, this rank is not recognized by the International Code of Botanical Nomenclature), the other three being Marattiopsida, Equisetopsida, and Psilotopsida.[1]

Classification

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The classification scheme proposed by Smith et al.(alternative names in brackets):


Discussion of Molecular Classification

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There has been some challenge to the recent molecular studies, claiming that these provide a skewed view of the phylogenetic order because the studies don't take into account fossil representatives[2]. However, the molecular studies have clarified relations among families that were thought to be non-monophyletic before the advent of molecular information, which were left in their non-monophyletic ranks because there was not enough information to do otherwise[3]. The reclassification of ferns using multiple molecular studies, which have generally supported each other, is not any different from classifications of the past--it is the definition of the relations utilizing the all the information available. It does not discourage the further study and clarification of the groups, and does not mean that if further study proves the classification wrong, it will not be changed.

Photos

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Taxonomy

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The Class Polypodiopsida is further organized into finer groupings including:

Orders

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Cyatheales

[more]

Gleicheniales

[more]

Hymenophyllales

[more]

Osmundales

Osmundaceae is the only family of the order Osmundales; an order in the class Polypodiopsida or in some classifications the only order in the class Osmundopsida. This is an ancient (known from the Upper Permian) and fairly isolated group that is often known as the "flowering ferns" because of the striking aspect of the ripe sporangia in Osmunda and Osmundastrum. 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. [more]

Polypodiales

The order Polypodiales encompasses the major lineages of polypod , 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. The characteristics of this group include: sporangia with a vertical annulus interrupted by the stalk and stomium; indusia laterally or centrally attached (or lost); gametophytes green, chordate, and surficial. [more]

Salviniales

A taxonomic order. [more]

Schizaeales

[more]

At least 11 species and subspecies belong to the Order Schizaeales.

More info about the Order Schizaeales may be found here.

References

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  1. ^ a b Smith, A. R., K. M. Pryer, et al. (2006). "A classification for extant ferns." Taxon 55(3): 705-731
  2. ^ Rothwell, G. W. and K. C. Nixon (2006). "How does the inclusion of fossil data change our conclusions about the phylogenetic history of euphyllophytes." Int. J. Plant Sci 167(3): 737-749
  3. ^ Kramer, K. U. (1990). Notes on the Higher Level Classification of the Recent Ferns. The Families and Genera of Vascular Plants: Pteridophytes and Gymnosperms. K. Kubitzki, K. U. Kramer and P. S. Green. New York, Springer-Verlag. 1: 49-52

Sources

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Last Revised: September 22, 2009
2009/09/22 06:36:47