The extant spermatophytes form five divisions, the first four of which are classified as gymnosperms, plants that have unenclosed, "naked seeds":[1]: 172 The fifth extant division is the flowering plants, also known as angiosperms or magnoliophytes, the largest and most diverse group of spermatophytes: In addition to the five living taxa listed above, the fossil record contains evidence of many extinct taxa of seed plants, among those: 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 the angiosperms radiated.

A series of evolutionary changes began with a whole genome duplication event in the ancestor of seed plants occurred about 319 million years ago.

[5] The spermatophytes were traditionally divided into angiosperms, or flowering plants, and gymnosperms, which includes the gnetophytes, cycads,[5] ginkgo, and conifers.

Older morphological studies believed in a close relationship between the gnetophytes and the angiosperms,[6] in particular based on vessel elements.

However, molecular studies (and some more recent morphological[7][8] and fossil[9] papers) have generally shown a clade of gymnosperms, with the gnetophytes in or near the conifers.