Eusporangiate fern

Eusporangiate ferns
Botrychium lunaria
Scientific classification
Kingdom:	Plantae
Division:	Pteridophyta
(unranked):	eusporangiate ferns
Classes
Psilotopsida Equisetopsida Marattiaceae

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 of spores (up to 7000 spores per sporangium in Christensenia)

There are four extant eusporangiate fern families, distributed among three classes. Each family is assigned to its own order.^[1][2]

• Class Psilotopsida
  • Order Psilotales, family Psilotaceae – Whisk ferns (2 genera, about 17 species)
  • Order Ophioglossales, family Ophioglossaceae – Adder’s-tongues (5 genera, about 80 species)
• Class Equisetopsida
  • Order Equisetales, family Equisetaceae – Horsetails (1 genus, about 15 species)
• Class Marattiopsida
  • Order Marattiales, family Marattiaceae – Marattoid ferns (6 genera, about 500 species)

The following diagram shows a likely phylogenic placement of eusporangiate fern classes within the vascular plants.^[3][4]

lycophytes (club mosses, spike mosses, quillworts) euphyllophytes spermatophytes (seed plants) ferns Psilotopsida  Psilotales (whisk ferns)   Ophioglossales (grapeferns etc.)  Equisetopsida  Equisetales (horsetails)  Marattiopsida  Marattiales  Polypodiopsida  Osmundales   Hymenophyllales   Gleicheniales   Schizaeales   Salviniales   Cyatheales   Polypodiales

eusporangiate ferns leptosporangiate ferns

Cladistics

While it is generally accepted that the leptosporangiate ferns are monophyletic, it is considered to be likely that the eusporangiate ferns, as a group, are paraphyletic.^[5] In each of the three examples from recently published studies, shown in the following table, it can be seen that, together, the four eusporangiate fern families do not form a single clade.

Pryer & Schuettpelz, 2009[6] ferns Ophioglossaceae Psilotaceae Equisetaceae Marattiaceae Leptosporangiate ferns

Rai & Graham, 2010[7] ferns Equisetaceae Ophioglossaceae Psilotaceae Marattiaceae Leptosporangiate ferns

Lehtonen, 2011[4] ferns Ophioglossaceae Psilotaceae Marattiaceae Equisetaceae Leptosporangiate ferns

References

1. Alan R. Smith; Kathleen M. Pryer; Eric Schuettpelz; Petra Korall; Harald Schneider; Paul G. Wolf (2006). "A classification for extant ferns" (PDF). Taxon. 55 (3): 705–731. doi:10.2307/25065646. Archived from the original (PDF) on February 26, 2008.
2. Maarten J. M. Christenhusz; Xian-Chun Zhang; Harald Schneider (2011). "A linear sequence of extant families and genera of lycophytes and ferns" (PDF). Phytotaxa. 19: 7–54.
3. Paul G. Wolf; Joshua P. Der; Jacob B. Davidson; Kathleen M. Pryer; Aaron M. Duffy; Amanda L. Grusz (2010). "The evolution of chloroplast genes and genomes in ferns" (PDF). Plant Molecular Biology. 76: 251–261. doi:10.1007/s11103-010-9706-4.
4. Samuli Lehtonen (2011). "Towards Resolving the Complete Fern Tree of Life" (PDF). PLoS ONE. 6 (10): e24851. doi:10.1371/journal.pone.0024851. PMC 3192703. PMID 22022365.
5. Kathleen M. Pryer; Eric Schuettpelz; Paul G. Wolf; Harald Schneider; Alan R. Smith; Raymond Cranfill (2004). "Phylogeny and evolution of ferns (monilophytes) with a focus on the early leptosporangiate divergences" (PDF). American Journal of Botany. 91 (10): 1582–1598. doi:10.3732/ajb.91.10.1582. PMID 21652310.
6. Kathleen M. Pryer; Eric Schuettpelz (2009). "Ferns" (PDF). In S. Blair Hedges; Sudhir Kumar. The Timetree of Life. Oxford Biology.
7. Hardeep S. Rai; Sean W. Graham (2010). "Utility of a large, multigene plastid data set in inferring higher-order relationships in ferns and relatives (Monilophytes)" (PDF). American Journal of Botany. 97 (9): 1444–1456. doi:10.3732/ajb.0900305.

• Hogan, C.Michael. 2010. Fern. Encyclopedia of Earth, National Council for Science and the Environment. topic ed. Saikat Basu
• Sporne, K. R. 1962. The morphology of pteridophytes, the structure of ferns and allied plants. pp. 127–135. Hutchison & Co. London.