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Seed-bearing plants were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetae, cycads, ginkgo, and conifers. Angiosperms are now thought to have evolved from a gymnosperm ancestor, which would make the gymnosperm taxon paraphyletic. Modern cladistics attempts to define taxa that are monophyletic, traceable to a common ancestor and inclusive therefore of all descendants of that common ancestor. Although not a monophyletic taxon, gymnosperm is still widely used to distinguish the four taxa of non-flowering, seed-bearing plants from the angiosperms.

A traditional classification grouped all the seed plants together as follows:

• Division Spermatophyta
  • Cycadopsida, the cycads
  • Ginkgoopsida, the ginkgo
  • Pinopsida, the conifers, ("Coniferopsida")
  • Gnetopsida, including GnetumGnetum is a genus of about 30-35 species of gymnosperms. They are tropical evergreen trees, shrubs and lianas. Species Gnetum subsect. Gnetum 2 species of trees; southeast Asia G. gnemon Gnetum subsect. Micrognemones 2 species of lianas; tropical west Afr, WelwitschiaWelwitschia mirabilis Welwitschia is a monotypic genus of succulent plant, consisting exclusively of the very odd Welwitschia mirabilis Hook. It is the only genus of the family Welwitschiacae in the order Welwitschiales (sometimes classified within order, EphedraSee text Ephedra is a genus of gymnosperm shrubs, the only genus in the family Ephedraceae and order Ephedrales . These plants occur in dry climates over a wide area mainly in the Northern Hemisphere, across southern Europe, north Africa, southwest and ce
  • Magnoliopsida, the flowering plantMagnoliopsida Dicots Liliopsida Monocots The flowering plants (also angiosperms or Magnoliophyta are one of the major groups of modern plants, comprising those that produce seeds in specialized reproductive organs called flowers, where the ovulary or carps, or Angiospermopsida

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 epoch. By the Triassic period, seed ferns had declined in importance, and gymnosperms were predominant until the Cretaceous, when the Angiosperms became predominant.

A more modern classification splits these groups into separate divisions (sometimes under the Superdivision Spermatophyta):

• Cycadophyta, the cycads
• Ginkgophyta, the ginkgo
• Pinophyta, the conifers
• Gnetophyta, including Gnetum, Welwitschia, Ephedra
• Magnoliophyta, the flowering plants