Gnetophyta is a division of plants, grouped within the gymnosperms (which also includes conifers, cycads, and ginkgos), that consists of some 70 species across the three relict genera: Gnetum (family Gnetaceae), Welwitschia (family Welwitschiaceae), and Ephedra (family Ephedraceae). Fossilized pollen attributed to a close relative of Ephedra has been dated as far back as the Early Cretaceous. Though diverse and dominant in the Paleogene and the Neogene, only three families, each containing a single genus, are still alive today. The primary difference between gnetophytes and other gymnosperms is the presence of vessel elements, a system of conduits that transport water within the plant, similar to those found in flowering plants. Because of this, gnetophytes were once thought to be the closest gymnosperm relatives to flowering plants, but more recent molecular studies have brought this hypothesis into question.
From Wikipedia article at https://en.wikipedia.org/wiki/Gnetopsida, which is released under the Creative Commons Attribution-Share-Alike License 3.0.
|Taxonomy (GBIF)||Life : Plantae : Tracheophyta : Gnetopsida|
|Taxonomy (PBDB)||Life : Plantae : Gnetophyta : Gnetopsida|
|Taxonomic Status (GBIF)||accepted|
|Taxon Size (PBDB)||4|
|Extant Size (PBDB)||1 (25%)|
|First Recorded Appearance||247 - 242 Ma|
|Primary Reference (PBDB)||D.J. Mabberley. 2000. The Plant-Book, 2nd ed. Cambridge University Press, Cambridge, UK, 858 p.|
|Name||Status||Common Name(s)||Fossil Occurrences||Oldest||Youngest|
|listed (PBDB)||9||247 Ma|
|Year||Name and Author|
|1884||Gnetopsida Kirpotenko pp. vii, 31|
|2001||Gnetopsida Doweld p. xix|