Spermatophyte

Taxobox
name = Seed Plants

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image_width = 200px
image_caption = "Welwitschia mirabilis" a member of the Gnetophyta
fossil_range = Devonian? or earlier to recent
regnum = Plantae
subdivision_ranks = Divisions
subdivision =
*Pinophyta
*Cycadophyta
*Ginkgophyta
*Gnetophyta
*Magnoliophyta
*Bennettitales†The spermatophytes (from the Greek word "Σπερματόφυτα") (also known as phanerogams) comprise those plants that produce seeds. They are a subset of the embryophytes or land plants. The living spermatophytes form five groups:

*cycads, a subtropical and tropical group of plants with a large crown of compound leaves and a stout trunk,
*"Ginkgo", a single living species of tree,
*conifers, cone-bearing trees and shrubs,
*gnetophytes, woody plants in the genera "Gnetum", "Welwitschia", and "Ephedra", and
*angiosperms, the flowering plants, a large group including many familiar plants in a wide variety of habitats.

In addition to the taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants. The so-called "seed ferns" (Pteridospermae) were one of the earliest successful groups of land plants, and forests dominated by seed ferns were prevalent in the late Paleozoic. "Glossopteris" was the most prominent tree genus in the ancient southern supercontinent of Gondwana during the Permian period. By the Triassic period, seed ferns had declined in ecological importance, and representatives of modern gymnosperm groups were abundant and dominant through the end of the Cretaceous, when angiosperms radiated. Another Late Paleozoic group of probable spermatophytes were the gigantopterids.

Relationships and nomenclature

Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads, ginkgo, and conifers. Older morphological studies have shown a close relationship between the gnetophytes and the angiosperms,cite journal | url = http://www.amjbot.org/cgi/content/full/91/10/1437 | title = The plant tree of life: an overview and some points of view | author = Jeffrey D. Palmer, Douglas E. Soltis and Mark W. Chase | journal = American Journal of Botany | year = 2004 | volume = 91 | pages = 1437–1445 | doi = 10.3732/ajb.91.10.1437] in particular based on vessel elements. However, molecular studies (and some more recent morphological [cite journal | journal = The Journal of the Torrey Botanical Society | pages = 169–209 | title = Seed ferns and the origin of angiosperms | author = James A. Doyle | volume = 133 | issue = 1 | month = January | year = 2006 | id = doi | id = 10.3159/1095-5674(2006)133%5B169:SFATOO%5D2.0.CO;2 | label = 10.3159/1095-5674(2006)133 [169:SFATOO] 2.0.CO;2 | year = 2006 | doi = 10.3159/1095-5674(2006)133 [169:SFATOO] 2.0.CO;2 ] and fossil [cite journal | url = http://aob.oxfordjournals.org/cgi/content/full/94/2/281 | title = A New Permian Gnetalean Cone as Fossil Evidence for Supporting Current Molecular Phylogeny | author = Zi-Qiang Wang | journal = Annals of Botany | year = 2004 | volume = 94 | issue = 2 | pages = 281–288 | doi = 10.1093/aob/mch138 | pmid = 15229124 ] papers) have generally shown a clade of gymnosperms, with the gnetophytes in or near the conifers. For example, one common proposed set of relationships is known as the "gne-pine hypothesis" and looks like: [Chaw, Shu-Miaw, Christopher L. Parkinson, Yuchang Cheng, Thomas M. Vincent, and Jeffrey D. Palmer. 2000. [http://www.pnas.org/cgi/content/full/97/8/4086 Seed plant phylogeny inferred from all three plant genomes: Monophyly of extant gymnosperms and origin of Gnetales from conifers] . "Proceedings of the National Academy of Sciences" 97: 4086-4091 ] [Bowe, L. Michelle, Gwénaële Coat, and Claude W. dePamphilis. 2000. [http://www.pnas.org/cgi/content/full/97/8/4092 Phylogeny of seed plants based on all three genomic compartments: Extant gymnosperms are monophyletic and Gnetales' closest relatives are conifers] . "Proceedings of the National Academy of Sciences" 97: 4092-4097.] [Soltis, Douglas E., Pamela S. Soltis and Michael J. Zanis. 2002. [http://intl.amjbot.org/cgi/content/full/89/10/1670 Phylogeny of seed plants based on evidence from eight genes] . "American Journal of Botany" 89: 1670-1681.]

clade
1=angiosperms
label2=gymnosperms
2=clade
1=cycads [cite journal | journal = Molecular Biology and Evolution | year = 2007 | volume = 24 | issue =6 | pages = 1366–1379 | doi = 10.1093/molbev/msm059 | title = Chloroplast Genome (cpDNA) of Cycas taitungensis and 56 cp Protein-Coding Genes of Gnetum parvifolium: Insights into cpDNA Evolution and Phylogeny of Extant Seed Plants | author = Chung-Shien Wu, Ya-Nan Wang, Shu-Mei Liu and Shu-Miaw Chaw | pmid = 17383970 ]
2="Ginkgo"
3=clade
1=clade
1=Pinaceae (the pine family)
2=gnetophytes
2=other conifers

The relationships between these groups should not be considered settled. [cite journal | title = Dating Dispersal and Radiation in the Gymnosperm Gnetum (Gnetales)—Clock Calibration When Outgroup Relationships Are Uncertain | author = Won, Hyosig; Renner, Susanne | journal = Systematic Biology | volume = 55 | issue = 4 | month = August | year = 2006 | pages = 610–622 | doi = 10.1080/10635150600812619 ]

A traditional classificationSpecify|date=February 2008 grouped put all the seed plants in a single division, with classes for our five groups:
*Division Spermatophyta
**Cycadopsida, the cycads
**Ginkgoopsida, the ginkgo
**Pinopsida, the conifers, ("Coniferopsida")
**Gnetopsida, the gnetophytes
**Magnoliopsida, the flowering plants, or Angiospermopsida

A more modern classification ranks these groups as separate divisions (sometimes under the Superdivision Spermatophyta):
*Cycadophyta, the cycads
*Ginkgophyta, the ginkgo
*Pinophyta, the conifers
*Gnetophyta, the gnetophytes
*Magnoliophyta, the flowering plants

References