Pteridosperm

{{Short description|Several distinct polyphyletic groups of extinct seed-bearing plants}} {{Paraphyletic group | auto = yes | fossil_range = {{Fossil range | 376 |50}} Late Devonian – Early Eocene | image = FossilFernLeavesPennsylvanianOhio.jpg | image_caption = Fossil seed fern leaves of ''Neuropteris'' (Medullosales) from the Late Carboniferous of northeastern Ohio. | taxon = Pteridospermatophyta | includes = * †Calamopityales * †Callistophytales * †Caytoniales * †Gigantopteridales * †Glossopteridales * †Lyginopteridales * †Medullosales * †Peltaspermales * †Corystospermales (also referred to as Umkomasiales) * †Petriellales | excludes_text = Excluded | excludes = * Angiospermae (flowering plants) * Cycadales (cycads) * Ginkgoales (ginkgos) * Pinophyta (conifers) * Gnetophyta * †Bennettitales * †Czekanowskiales * †Cordaitales | image2 = Lepidopteris life restoration.jpg | image2_caption = Life restoration of ''Lepidopteris'' (Peltaspermales) | synonyms = Pteridospermatopsida }}

'''Pteridosperms''', also known as '''seed ferns''', are a polyphyletic<ref>{{Cite journal |last1=Elgorriaga |first1=Andrés |last2=Escapa |first2=Ignacio H. |last3=Cúneo |first3=N. Rubén |date=July 2019 |title=Relictual Lepidopteris (Peltaspermales) from the Early Jurassic Cañadón Asfalto Formation, Patagonia, Argentina |url=https://www.journals.uchicago.edu/doi/10.1086/703461 |journal=International Journal of Plant Sciences |language=en |volume=180 |issue=6 |pages=578–596 |doi=10.1086/703461 |issn=1058-5893 |url-access=subscription}}</ref> grouping of extinct seed-producing plants. The earliest fossil evidence for plants of this type are the lyginopterids of late Devonian age.<ref name="Rothwelletal989">{{Cite journal |last1=Rothwell G. W. |last2=Scheckler S. E. |last3=Gillespie W. H. |year=1989 |title=''Elkinsia'' gen. nov., a Late Devonian gymnosperm with cupulate ovules |journal=Botanical Gazette |volume=150 |issue=2 |pages=170–189 |doi=10.1086/337763 |s2cid=84303226}}</ref> They flourished particularly during the Carboniferous and Permian periods. Pteridosperms declined during the Mesozoic Era and had mostly disappeared by the end of the Cretaceous Period, though ''Komlopteris'' seem to have survived into Eocene times, based on fossil finds in Tasmania.<ref name="McLoughlinetal2008">{{Cite journal |last1=McLoughlin S. |last2=Carpenter R.J. |last3=Jordan G.J. |last4=Hill R.S. |year=2008 |title=Seed ferns survived the end-Cretaceous mass extinction in Tasmania |url=http://urn.kb.se/resolve?urn=urn:nbn:se:nrm:diva-319 |journal=American Journal of Botany |volume=95 |issue=4 |pages=465–471 |doi=10.3732/ajb.95.4.465 |pmid=21632371 |doi-access=free}}</ref>

With regard to the enduring utility of this division, many palaeobotanists still use the pteridosperm grouping in an informal sense to refer to the seed plants that are not angiosperms, coniferoids (conifers or cordaites), ginkgophytes (ginkgos or czekanowskiales), cycadophytes (cycads or bennettites), or gnetophytes. This is particularly useful for extinct seed plant groups whose systematic relationships remain speculative, as they can be classified as pteridosperms with no invalid implications being made as to their systematic affinities. Also, from a purely curatorial perspective the term pteridosperms is a useful shorthand for describing the fern-like fronds that were probably produced by seed plants, which are commonly found in many Palaeozoic and Mesozoic fossil floras.

==History of classification== [[File:Bulgo Sandstone biota.jpg|thumb|Life restoration of the seed fern ''Dicroidium'' (Corystospermales/Umkomasiales, top right), in an Early Triassic Australian landscape]] The concept of pteridosperms goes back to the late 19th century when palaeobotanists came to realise that many Carboniferous fossils resembling fern fronds had anatomical features more reminiscent of the modern-day seed plants, the cycads. In 1899 the German palaeobotanist Henry Potonié coined the term "''Cycadofilices''" ("cycad-ferns") for such fossils, suggesting that they were a group of non-seed plants intermediate between the ferns and cycads.<ref name="Potonie1899">{{Cite book |last=Potonié |first=H. |title=Lehrbuch der Pflanzenpaläontologie |year=1899 |location=Berlin, DE |lang=de}}</ref> Shortly afterwards, the British palaeobotanists Frank Oliver and Dukinfield Henry Scott (with the assistance of Oliver's student at the time, Marie Stopes) made the critical discovery that some of these fronds (genus ''Lyginopteris'') were associated with seeds (genus ''Lagenostoma'') that had identical and very distinctive glandular hairs, and concluded that both fronds and seeds belonged to the same plant.<ref name="OliverScott1904">{{Cite journal |last1=Oliver, F.W. |last2=Scott, D.H. |year=1904 |title=On the structure of the Palaeozoic seed ''Lagenostoma Lomaxi'', with a statement of the evidence upon which it is referred to ''Lyginodendron'' |journal=Philosophical Transactions of the Royal Society of London |series=Series B |volume=197 |issue=225–238 |pages=193–247 |doi=10.1098/rstb.1905.0008 |doi-access=free}}</ref> Soon, additional evidence came to light suggesting that seeds were also attached to the Carboniferous fern-like fronds ''Dicksonites'',<ref name="Grandeury1904">{{Cite journal |last=Grand'Eury C |year=1904 |title=Sur les graines Neuropteridées |journal=Comptes Rendus de l'Académie des Sciences de Paris |volume=140 |pages=782–786}}</ref> ''Neuropteris''<ref name="Kidston1904">{{Cite journal |last=Kidston R |year=1904 |title=On the fructification of ''Neuropteris heterophylla'', Brongniart |journal=Philosophical Transactions of the Royal Society of London, Series B |volume=197 |issue=225–238 |pages=1–5 |doi=10.1098/rstb.1905.0001}}</ref> and ''Aneimites''.<ref name="White1904">{{Cite journal |last=White D |year=1904 |title=The seeds of ''Aneimites'' |journal=Smithsonian Institution, Miscellaneous Collection |volume=47 |pages=322–331}}</ref> Initially it was still thought that they were "transitional fossils" intermediate between the ferns and cycads, and especially in the English-speaking world they were referred to as "seed ferns" or "pteridosperms". Today, despite being regarded by most palaeobotanists as only distantly related to ferns, these spurious names have nonetheless established themselves. Nowadays, four orders of Palaeozoic seed plants tend to be referred to as pteridosperms: Lyginopteridales, Medullosales, Callistophytales and Peltaspermales, with "Mesozoic seed ferns" including the Petriellales, Corystospermales and Caytoniales.<ref>Taylor, Edith L., et al. "Mesozoic Seed Ferns: Old Paradigms, New Discoveries." ''The Journal of the Torrey Botanical Society'', vol. 133, no. 1, 2006, pp. 62–82. ''JSTOR'', {{JSTOR|20063823}}. Accessed 24 Sept. 2023.</ref>

Their discovery attracted considerable attention at the time, as the pteridosperms were the first extinct group of vascular plants to be identified solely from the fossil record. In the 19th century the Carboniferous Period was often referred to as the "Age of Ferns" but these discoveries during the first decade of the 20th century made it clear that the "Age of Pteridosperms" was perhaps a better description.{{cn|date=June 2025}}

During the 20th century the concept of pteridosperms was expanded to include various Mesozoic groups of seed plants with fern-like fronds, such as the Corystospermaceae. Some palaeobotanists also included seed plant groups with entire leaves such as the Glossopteridales and Gigantopteridales, which was stretching the concept. In the context of modern phylogenetic models,<ref name="HiltonBateman2006">{{Citation |last1=Hilton, J. |title=Pteridosperms are the backbone of seed-plant phylogeny |journal=Journal of the Torrey Botanical Society |volume=33 |pages=119–168 |year=2006 |doi=10.3159/1095-5674(2006)133[119:PATBOS]2.0.CO;2 |s2cid=86395036 |name-list-style=amp |last2=Bateman, R. M.}}</ref> the groups often referred to as pteridosperms appear to be liberally spread across a range of clades, and many palaeobotanists today would regard pteridosperms as little more than a paraphyletic 'grade-group' with no common lineage.{{clarification needed|reason=A paraphyletic group is part of a common lineage, it just excludes some ancestral groups. Should it be polyphyletic here? |date=March 2023}} One of the few characters that may unify the group is that the ovules were borne in a cupule, a group of enclosing branches, but this has not been confirmed for all "pteridosperm" groups.{{cn|date=June 2025}}

It has been speculated that some seed fern groups may be close to the ancestry of flowering plants (angiosperms). A 2009 study concluded that "phylogenetic analysis techniques have surpassed the hard data needed to formulate meaningful phylogenetic hypotheses" regarding the relationships of "seed ferns" to living plant groups.<ref>{{Cite journal |last1=Taylor |first1=Edith L. |last2=Taylor |first2=Thomas N. |date=January 2009 |title=Seed ferns from the late Paleozoic and Mesozoic: Any angiosperm ancestors lurking there? |url=https://bsapubs.onlinelibrary.wiley.com/doi/10.3732/ajb.0800202 |journal=American Journal of Botany |language=en |volume=96 |issue=1 |pages=237–251 |doi=10.3732/ajb.0800202 |issn=0002-9122 |pmid=21628187 |url-access=subscription}}</ref>

==Taxonomy== === Major groups === {{Unreferenced section|date=March 2026}} * Order †Calamopityales Němejc (1963) * Order †Corystospermales Petriella (1981) [= Umkomasiales Doweld (2001)] * Order †Callistophytales Rothwell (1981) emend. Anderson, Anderson & Cleal (2007) [Poroxylales Němejc (1968)] * Order †Petriellales Taylor et al. (1994) * Order †Peltaspermales Taylor (1981) [Lepidopteridales Němejc (1968)] * Order †Gigantopteridales Li & Yao (1983) [Gigantonomiales Meyen (1987)] * Order †Pentoxylales Pilger & Melchior (1954) * Order †Glossopteridales Plumstead, 1956 * Order †Caytoniales Gothan (1932) * Order †Medullosales Corsin (1960) * Order †Lyginopteridales (Corsin (1960)) Havlena (1961) [Lagenostomatales Seward ex Long (1975); Lyginodendrales Nemejc (1968); Sphenopteridales Schimper 1869] ** Family †Angaranthaceae Naugolnykh (2012) ** Family †Heterangiaceae Němejc (1950) nom. nud. ** Family †Physostomataceae Long (1975) ** Family †Lyginopteridaceae Potonie (1900) emend. Anderson, Anderson & Cleal (2007) [Lagenostomataceae Long (1975; Pityaceae Scott (1909); Lyginodendraceae Scott (1909); Sphenopteridaceae Gopp. (1842); Pseudopecopteridaceae Lesquereux (1884); Megaloxylaceae Scott (1909), nom. rej.; Rhetinangiaceae Scott (1923), nom. rej.; Tetratmemaceae Němejc (1968)] ** Family †Moresnetiaceae Němejc (1963) emend. Anderson, Anderson & Cleal (2007) [Genomospermaceae Long (1975); Elkinsiaceae Rothwell, Scheckler & Gillespie (1989) ex Cleal; Hydraspermaceae]

=== Other minor groups === * Class ''incertae sedis'' ** Order ''incertae sedis'' *** Family ?†Nystroemiaceae Wang & Pfefferkorn (2009)<ref>{{Cite journal |last1=Wang |first1=Jun |last2=Pfefferkorn |first2=Hermann W. |date=2010-01-22 |title=Nystroemiaceae, a new family of Permian gymnosperms from China with an unusual combination of features |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=277 |issue=1679 |pages=301–309 |doi=10.1098/rspb.2009.0913 |issn=0962-8452 |pmc=2842674 |pmid=19656793}}</ref> **** †''Nystroemia'' Halle (1927) *** Family †Austrocalyxaceae Vega & Archangelsky (2001)<ref>{{Cite journal |last1=Vega |first1=Juan Carlos |last2=Archangelsky |first2=Sergio |date=2001-04-25 |title=Austrocalyxaeae, a new pteridoserm family from Gondwana |url=https://www.schweizerbart.de/papers/palb/detail/257/72575 |journal=Palaeontographica Abteilung B |language=en |volume=257 |issue=1–6 |pages=1–16 |bibcode=2001PalAB.257....1V |doi=10.1127/palb/257/2001/1 |s2cid=248282839 |url-access=subscription}}</ref> **** †''Austrocalyx'' **** †''Polycalyx'' **** †''Rinconadia'' **** †''Jejenia'' **** †''Fedekurtzia'' (Archangelsky) emend. Coturel et Césari, 2017 ** Order ?†Alexiales Anderson & Anderson (2003)<ref name="Anderson-2003">{{Cite journal |last1=Anderson |first1=John M. |last2=Anderson |first2=Heidi M. |date=2003 |title=Heyday of the gymnosperms: systematics and biodiversity of the Late Triassic Molteno fructifications. |url=https://archive.org/details/heydayofgymnospe15ande/mode/2up |journal=Strelitzia |volume=15 |pages=1–308}}</ref> *** Family †Alexiaceae Anderson & Anderson (2003) **** †''Alexia'' Anderson & Anderson (2003) ** Order †Buteoxylonales *** Family †Buteoxylonaceae Barnard & Long (1973)<ref>{{Cite journal |last1=Barnard |first1=P. D. W. |last2=Long |first2=A. G. |date=1973 |title=4.—On the Structure of a Petrified Stem and some Associated Seeds from the Lower Carboniferous Rocks of East Lothian, Scotland |url=https://www.cambridge.org/core/product/identifier/S008045680001499X/type/journal_article |journal=Transactions of the Royal Society of Edinburgh |language=en |volume=69 |issue=4 |pages=91–108 |doi=10.1017/S008045680001499X |issn=0080-4568 |s2cid=129792299 |url-access=subscription}}</ref> **** †''Buteoxylon'' Barnard & Long (1973) **** †''Triradioxylon'' Barnard & Long (1975)<ref>{{Cite journal |last1=Barnard |first1=P. D. W. |last2=Long |first2=A. G. |date=1975 |title=10.—Triradioxylon—a New Genus of Lower Carboniferous Petrified Stems and Petioles together with a Review of the Classification of Early Pterophytina |url=https://www.cambridge.org/core/product/identifier/S0080456800015179/type/journal_article |journal=Transactions of the Royal Society of Edinburgh |language=en |volume=69 |issue=10 |pages=231–249 |doi=10.1017/S0080456800015179 |issn=0080-4568 |url-access=subscription}}</ref> ** Order †Dicranophyllales Meyen (1984) emend. Anderson, Anderson & Cleal (2007) *** Family †Dicranophyllaceae Němejc (1959) ex Archangelsky & Cúneo (1990) *** Family †Trichopityaceae Němejc (1968) [Florin emend.] *** †''Polyspermophyllum''? Archangelsky and Cúneo (1990) (possibly a coniferophyte) ** Order †Erdtmanithecales Friis and Pedersen (1996) ** Order †Fredlindiales Anderson & Anderson (2003)<ref name="Anderson-2003" /> ** Order †Hamshawviales Anderson & Anderson (2003)<ref name="Anderson-2003" /> ** Order †Hlatimbiales Anderson & Anderson (2003)<ref name="Anderson-2003" /> *** Family †Hlatimbiaceae Anderson & Anderson (2003) **** †''Hlatimbia'' Anderson & Anderson (2003) **** †''Batiopteris'' Anderson & Anderson (2003) ** Order †Matatiellales Anderson & Anderson (2003)<ref name="Anderson-2003" /> ** Order †Nilssoniales Darrah (1960) (possibly cycadopsids) ** Order †Phasmatocycadales Doweld (2001) [Taeniopteridales] *** Family †Phasmatocycadaceae Doweld (2001) [Spermopteridaceae Doweld (2001)] **** †''Lesleya'' Lesquereux (1879–80) (otherwise placed as incetae sedis regarding family and order) * Class †Axelrodiopsida Anderson & Anderson (2007)<ref>{{Cite journal |last1=Anderson |first1=John M. |last2=Anderson |first2=Heidi M. |last3=Cleal |first3=Chris J. |date=2007 |title=Brief history of the gymnosperms: classification, biodiversity, phytogeography and ecology |url=http://opus.sanbi.org/bitstream/20.500.12143/5611/1/Strelitzia_20_2007.pdf |journal=Strelitzia |volume=20 |pages=1–280}}</ref> ** Order †Axelrodiales Anderson & Anderson (2007) *** Family †Axelrodiaceae Anderson & Anderson (2007) **** †''Axelrodia'' Cornet (1986) **** †''Sanmiguelia'' Brown (1956) **** †''Synangispadixis'' Cornet (1986) *** Family †Zamiostrobacea Anderson & Anderson (2007) **** †''Zamiostrobus'' Endlicher (1836) * Incertae sedis to order and family: ** †''Gnetopsis'' Renault et Zeiller (1884) ** †''Pullaritheca'' Rothwell and Wight (1989) ** †''Kegelidium'' Dolianiti (1954) ** †''Ptilozamites'' ** †''Pitus'' (also known as ''Pitys'')

==References== {{Reflist}}

== External links == * [https://web.archive.org/web/20050610075505/http://taggart.glg.msu.edu/bot335/sfern.htm Seed fern paleontology] * [https://www.uni-muenster.de/GeoPalaeontologie/Palaeo/Palbot/seite9.html Seed ferns]

Category:Pteridospermatophyta Category:Plant divisions Category:Prehistoric plants Category:Devonian plants Category:Carboniferous plants Category:Permian plants Category:Triassic plants Category:Jurassic plants Category:Cretaceous plants Category:Paleocene plants Category:Eocene plants Category:Devonian first appearances Category:Eocene extinctions Category:Paraphyletic groups