Belongs within: Spermatophyta.
Contains: Gnetophyta.
The Pan-Gnetophyta are the total clade of all plants more closely related to modern gnetophytes than other plants (Cantino et al. 2007). Candidate representatives are united by the possession of seeds with an outer envelope and the integument extended into a long, narrow micropylar tube (Friis et al. 2007). These include the Erdtmanithecales, Cretaceous plants known from reproductive structures and seeds associated with Eucommiidites pollen; vegetative structures have not yet been identified for the group. The Bennettitales were a group of superficially cycad-like plants that lived during the Mesozoic. Bennettitales had superficially flower-like reproductive structures that have led some authors to consider them more closely related to flowering plants.
<==Pan-Gnetophyta [Gnetopsida]CD07
|--ErdtmanithecalesFC07
| |--Erdtmanispermum balticumFC07
| |--Erdtmanitheca texensisFC07
| |--Eucommiitheca hirsutaFC07
| |--Bayeritheca hughesiiFC07
| |--EucommiiditesFC07
| | |--E. minor Groot & Penny 1960I02
| | `--E. troedsonii Erdtmann 1948I02
| `--SpermatitesFC07
| |--S. pattensisFC07
| `--S. patuxensisFC07
|--+--PiroconitesD98
| `--Gnetales [Gnetidra]FC07
| | i. s.: Ephedrites Goeppert & Berendt in Berendt 1845KDD98
| | `--E. sinensisKDD98
| | GurvanellaZBH03
| | Chaoyangia liangii Duan 1998ZBH03
| | BaisianthusZ02
| | Problematospermum ovaleRL09
| | Leongathia Krassilov, Dilcher & Douglas 1998KDD98
| | `--*L. elegans Krassilov, Dilcher & Douglas 1998KDD98
| | EoanthaKDD98
| | HeeralaKDD98
| | Aegianthus sibiricumPL12
| | Schilderia adamanica Daugherty 1934CA04
| |--Dechellyia gormanii Ash 1972D98, C93
| `--GnetophytaFC07
`--BennettitalesFC07
| i. s.: Weltrichia regalisG10
| SturiellaZ02
| Zamites gigasGT02, T13 [=Williamsonia gigasT13]
| Vardekloeftia sulcata [incl. V. conica]FC07
| Cycadeoidella japonicaFC07
| WilliamsoniellaPL12
| |--W. coronataPL12
| `--W. karataviensisG10
`--Bennettitaceae [Cycadeoidaceae, Williamsoniaceae]C93
|--Bennettites crossospermusFC07
|--Haitingeria krasseri (Schuster) Krasser 1919C93
|--Leguminanthus siliquosus (Leuthardt) Kräusel & Schaarschmidt 1966C93
|--Westersheimia pramelreuthensis Krasser 1919C93
|--Sturianthus langeri Kräusel 1949C93
|--Bennetticarpus wettsteinii (Krasser) Kräusel 1949C93
|--Leuthardtia ovalis Kräusel & Schaarschmidt 1966C93
|--Monanthesia magnifica Wieland ex Delevoryas 1959C93
|--PterophyllumC93
| |--P. carbonicumG31
| `--P. nathorsti [=Dioonites nathorsti]T30
|--WilliamsoniaFC07
| |--W. bockiiFC07
| |--W. himasFC07
| |--W. scoticaFC07
| |--W. sewardianaFC07
| |--W. spectabilisT13
| `--W. whitbiensisT13
`--CycadeoideaFC07
|--C. albiana [=Bennettites albianus]FC07
|--C. dacotensisFC07
|--C. dartoniFC07
|--C. gibsonianaFC07
|--C. maccafferyiFC07
`--C. morierei [=Williamsonia morierei, Bennettites morierei]FC07
*Type species of generic name indicated
References
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[C93] Cleal, C. J. 1993. Gymnospermophyta. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 795–808. Chapman & Hall: London.
[CA04] Creber, G. T., & S. R. Ash. 2004. The Late Triassic Schilderia adamanica and Woodworthia arizonica trees of the Petrified Forest National Park, Arizona, USA. Palaeontology 47: 21–38.
[D98] Doyle, J. A. 1998. Phylogeny of vascular plants. Annual Review of Ecology and Systematics 29: 567–599.
[FC07] Friis, E. M., P. R. Crane, K. R. Pedersen, S. Bengtson, P. C. J. Donoghue, G. W. Grimm & M. Stampanoni. 2007. Phase-contrast X-ray microtomography links Cretaceous seed with Gnetales and Bennettitales. Nature 450: 549–552.
[GT02] Gomez, B., F. Thévenard, M. Fantin & L. Guisberti. 2002. Late Cretaceous plants from the Bonarelli Level of the Venetian Alps, northeastern Italy. Cretaceous Research 23: 671–685.
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[G31] Grabau, A. W. 1931. The Permian of Mongolia: A report on the Permian fauna of the Jisu Honguer limestone of Mongolia and its relations to the Permian of other parts of the world. American Museum of Natural History: New York.
[I02] Ibrahim, M. I. A. 2002. Late Albian-Middle Cenomanian palynofacies and palynostratigraphy, Abu Gharadig-5 well, Western Desert, Egypt. Cretaceous Research 23: 775–788.
[KDD98] Krassilov, V. A., D. L. Dilcher & J. G. Douglas. 1998. New ephedroid plant from the Lower Cretaceous Koonwarra fossil bed, Victoria, Australia. Alcheringa 22 (2): 123–133.
[PL12] Peñalver, E., C. C. Labandeira, E. Barrón, X. Delclòs, P. Nel, A. Nel, P. Tafforeau & C. Soriano. 2012. Thrips pollination of Mesozoic gymnosperms. Proceedings of the National Academy of Sciences of the USA 109 (22): 8623–8628.
[RL09] Ren, D., C. C. Labandeira, J. A. Santiago-Blay, A. Rasnitsyn, C. Shih, A. Bashkuev, M. A. V. Logan, C. L. Hotton & D. Dilcher. 2009. A probable pollination mode before angiosperms: Eurasian, long-proboscid scorpionflies. Science 326: 840–847.
[T13] Thomas, H. H. 1913. The fossil flora of the Cleveland district of Yorkshire: I—The flora of the Marske quarry. With notes on the stratigraphy, by the Rev. George Johne Lane, F.G.S. Annals and Magazine of Natural History, series 8, 12: 150.
[T30] Thomas, H. H. 1930. Further observations on the cuticle structure of Mesozoic cycadean fronds. Proceedings of the Linnean Society of London 141: 5–7.
[Z02] Zherikhin, V. V. 2002. Ecological history of the terrestrial insects. In: Rasnitsyn, A. P., & D. L. J. Quicke (eds) History of Insects pp. 331–388. Kluwer Academic Publishers: Dordrecht.
[ZBH03] Zhou, Z., P. M. Barrett & J. Hilton. 2003. An exceptionally preserved Lower Cretaceous ecosystem. Nature 421: 807–814.