Pteridospermatophyta

The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") refers to several distinct polyphyletic groups of extinct seed-bearing plants (spermatophytes). The earliest fossil evidence for plants of this type is the genus Elkinsia of the late Devonian age.[1] 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 some pteridosperm-like plants seem to have survived into Eocene times, based on fossil finds in Tasmania.[2]

Pteridospermatophyta
Temporal range: 376 – 66 Ma Late Devonian – End Cretaceous (Possible Eocene survival)
Fossil seed fern leaves from the Late Carboniferous of northeastern Ohio.
Scientific classification
Kingdom: Plantae
(unranked): Polysporangiophytes
(unranked): Tracheophytes
(unranked): Spermatophytes
Groups included
Excluded

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.[3] 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.[4] Soon, additional evidence came to light suggesting that seeds were also attached to the Carboniferous fern-like fronds Dicksonites,[5] Neuropteris[6] and Aneimites.[7] 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.

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.

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,[8] 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. 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.

With regard to the enduring value of the 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 or cycadophytes (cycads or bennettites). This is particularly useful for extinct seed plant groups whose systematic relationships remain speculative, as they can be classified as pteridosperms with no valid 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.

Phylogeny

An alternative phylogeny of spermatophytes based on the work by Novíkov & Barabaš-Krasni 2015[9] with plant taxon authors from Anderson, Anderson & Cleal 2007[10] showing the relationship of extinct clades.

Spermatophytina
 

†Moresnetiopsida Doweld (2001)

 
 
 

†Lyginopteridopsida Novák (1961) emend. Anderson, Anderson & Cleal (2007)

 
 
 

†Pachytestopsida Doweld (2001)

 
 
 

†Callistophytales Rothwell (1981) emend. Anderson, Anderson & Cleal (2007)

 
 
 

†Peltaspermopsida Doweld (2001)

 
 
 

†Umkomasiales Doweld (2001)

 
 
 
 

†Phasmatocycadopsida Doweld (2001)

 
 
 
 

†Pentoxylopsida Pant ex Doweld (2001)

 
 

†Dictyopteridiopsida Doweld (2001)

 
 
 
 

†Cycadeoideopsida Scott (1923)

 
 
 

†Caytoniopsida Thomas ex Frenguelli (1946)

 
 

Magnoliopsida (Flowering plants)

 
 
 
 
 
Acrogymnospermae
 

Cycadopsida (Cycads)

 
 
 

Ginkgoopsida (Maidenhair trees)

 
 

Pinopsida (Conifers)

 
 
 
 
 
 
 
 
 
 
Seed ferns

Taxonomy
Pteridospermatophyte fossil
  • Family ?†Avatiaceae Anderson & Anderson (2003)
  • Order ?†Alexiales Anderson & Anderson (2003)
    • Family †Alexiaceae Anderson & Anderson (2003)
  • Order ?†Hamshawviales Anderson & Anderson (2003)
    • Family †Hamshawviaceae Anderson & Anderson (2003)
  • Order ?†Hexapterospermales Doweld (2001)
    • Family †Colpospermaceae Doweld (2001)
    • Family †Hexapterospermaceae Doweld (2001) nom cons. [Potonieaceae (Halle (1933)) Remy & Remy (1959) emend. Anderson & Anderson (2007)]
  • Order ?†Hlatimbiales Anderson & Anderson (2003)
    • Family †Hlatimbiaceae Anderson & Anderson (2003)
  • Order ?†Matatiellales Anderson & Anderson (2003)
    • Family †Matatiellaceae Anderson & Anderson (2003)
  • Order ?†Petriellales Taylor et al. (1994)
    • Family †Petriellaceae Taylor, del Fueyo & Taylor (1994)
    • Family †Kannaskoppiaceae Anderson & Anderson (2003)
  • Order †Umkomasiales Doweld (2001) [Corystospermales; Corystophytina]
    • Family †Angaropeltidaceae Doweld (2001)
    • Family †Umkomasiaceae Petriella (1981) (Corystospermaceae (Thomas (1933)) Stockey & Rothwel nom. illeg.; Zuberiaceae Němejc (1968)]
  • Class ?†Arberiopsida Doweld (2001) [Clealopsida]
    • Order †Dicranophyllales Meyen (1984) emend. Anderson, Anderson & Cleal (2007)
      • Family †Dicranophyllaceae Archangelsky & Cúneo (1990
    • Order †Aberiales Meyen (1984) [Noeggerathopsidales Nemejc (1968)]
      • Family †Schmeissneriaceae Zhou (1997)
      • Family †Arberiaceae (Rigby (1972) Anderson & Anderson (1985) [Noeggerathopsidaceae Feistmantel (1879)]
  • Class ?†Axelrodiopsida Anderson & Anderson
    • Order †Axelrodiales Anderson & Anderson (2007)
      • Family †Zamiostrobacea Anderson & Anderson (2007)
      • Family †Axelrodiaceae Anderson & Anderson (2007)
  • Class †Moresnetiopsida Doweld (2001) [Moresnetiophyta Doweld (2001); Elkinsiophytina]
    • Order †Calamopityales Němejc (1963)
      • Family †Calamopityaceae (Solm. (1896)) Scott (1909) [Buteoxylaceae Barnard & Long (1973); Stenomyelaceae Scott (1923); Buteoxylonaceae]
    • Order †Tetrastichiales Němejc (1968)
      • Family †Tetrastichiaceae Němejc (1968)
    • Order †Pullarithecales Doweld (1998)
      • Family †Gnetopsidaceae Doweld (2001)
      • Family †Pullarithecaceae Doweld (1998
      • Family †Calathiopsidaceae Doweld (2001)
      • Family †Austrocalyxaceae Vega & Archangelsky (2001)
    • Order †Moresnetiales Doweld (2001)
      • Family †Eurystomataceae Long (1975)
      • Family †Eospermatacesidae Long (1975)
      • Family †Moresnetiaceae Němejc (1963) emend. Anderson, Anderson & Cleal (2007) [Genomospermaceae Long (1975); Elkinsiaceae Rothwell, Scheckler & Gillespie (1989) ex Cleal; Hydraspermaceae]
  • Class †Lyginopteridopsida Novák (1961) emend. Anderson, Anderson & Cleal (2007) [Lagenostomatopsida Cleal (1993); Lyginopteridophyta Doweld (2001); Lyginopteridophytina]
    • Order †Lyginopteridales (Corsin (1960)) Havlena (1961) [Lagenostomatales Seward ex Long (1975); Lyginodendrales Nemejc (1968); Pityales]
      • 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)]
  • Class †Pachytestopsida Doweld (2001) [Medullosopsida nom. nud.; Trigonocarpopsida nom. nud.; Medullosae]
    • Order †Codonospermales Doweld (2001)
      • Family †Codonospermaceae Doweld (2001) emend. Anderson, Anderson & Cleal (2007)
    • Order †Pachytestales Doweld (2001) (Medullosales Corsin (1960); Trigonocarpales nom. inv.; Neuropteridales]
      • Family †Potonieaceae Halle (1933) emend. Anderson, Anderson & Cleal (2007) [Rachivestitaceae; Perispermaceae]
      • Family †Polylophospermaceae Doweld (2001) emend. Anderson, Anderson & Cleal (2007)
      • Family †Stephanospermaceae Doweld (2001) emend. Anderson, Anderson & Cleal (2007)
      • Family †Neurodontopteridaceae Laveine (1966) [incl. Odontopteridaceae Trapl (1926) sensu Corsin (1960)]
      • Family †Pachytestaceae Doweld (2001) [Medullosaceae (Gopp. (1842)) Sterzel (1896); Whittleseyaceae Remy & Remy (1959); Callipteridaceae Corsin ex Wagner (1965); Callipteridiaceae; Callipteraceae; Protoblechnidaceae]
      • Family †Alethopteridaceae (Lesquereux (1884)) Corsin (1960) emend. Anderson, Anderson & Cleal (2007)
      • Family †Cyclopteridaceae Corsin ex Wagner (1964)
  • Class †Callistophytopsida [Callistophytina]
    • Order †Callistophytales Rothwell (1981) emend. Anderson, Anderson & Cleal (2007) [Poroxylales Němejc (1968)]
      • Family †Cornucarpaceae Doweld (2001) [Eremopteridaceae]
      • Family †Callistophytaceae Stidd & Hall (1970), nom. cons. [Mariopteridaceae Němejc (1968); Callospermariaceae Long (1975); Poroxylaceae Scott (1923)]
  • Class †Peltaspermopsida Doweld (2001) [Peltaspermidae Němejc (1968); Peltaspermophyta Doweld (2001) s.s.; Peltaspermae]
    • Order †Sporophyllitales Doweld (2001)
      • Family †Sporophyllitaceae Doweld (2001)
      • Family †Leuthardtiaceae Doweld (2001)
    • Order †Trichopityales Doweld (2001) [Psygmophyllales Nakai (1943)]
      • Family †Trichopityaceae Němejc (1968) [Florin emend.]
      • Family †Psygmophyllaceae Zalessky (1937) emend. Naugolnykh [Syniopteridaceae Petrescu & Dragastan (1981)]
    • Order †Peltaspermales Taylor (1981) [Lepidopteridales Němejc (1968)]
      • Family †Cardiolepidaceae Meyen (1977)
      • Family †Autuniaceae Doweld (2001)
      • Family †Peltaspermaceae (Thomas (1933)) Pilger & Melchoir (1954)) [Cycadopteridaceae Laguzen (1887); Thinnfeldiaceae Zimmerman (1959); Compsopteridaceae Petrescu & Dragastan (1981)]
  • Class †Phasmatocycadopsida Doweld (2001)
    • Order †Phasmatocycadales Doweld (2001) [Taeniopteridales]
      • Family †Phasmatocycadaceae Doweld (2001) [Spermopteridaceae Doweld (2001); Taeniopteridaceae Schimper (1869), nom rej.]
    • Order †Gigantopteridales Li & Yao (1983) [Gigantonomiales Meyen (1987)]
      • Family †Emplectopteridaceae Wagner (1967)
      • Family †Gigantopteridaceae Koidzumi (1936) [Cardioglossaceae Koidzumi ex Jongmans (1958); Gigantonomiaceae Meyen (1987)]
  • Class †Pentoxylopsida Pant ex Doweld (2001) [Pentoxylophytina Lemoigne (1988); Pentoxyla]
    • Order †Pentoxylales Pilger & Melchior (1954)
      • Family †Lindthecaceae Anderson & Anderson (2003)
      • Family †Pentoxylaceae Pilger & Melchior (1954) [Pentoxyleae Sahni (1948)]
  • Class †Dictyopteridiopsida Doweld (2001) [Ottokariopsida Anderson & Anderson (2007); Glossopteridophytina Lemoigne (1988)]
    • Order †Dictyopteridiales McLoughlin ex Doweld (2001) [Ottokariales Anderson & Anderson (1985)]
      • Family †Breyteniaceae Doweld (2001)
      • Family †Dictyopteridiaceae Rigby (1978) [Ottokariaceae Anderson & Anderson (1985); Scutaceae Rigby (1978), nom. illeg.]
    • Order †Lidgettoniales Doweld (2001)
      • Family †Denkaniaceae Doweld (2001)
      • Family †Parthaceae Doweld (2001)
      • Family †Lidgettoniaceae Anderson & Anderson (1985)
    • Order †Rigbyales Doweld (2001) (Glossopteridales Luber & Schwedov (1963), nom. rej.]
      • Family †Rigbyaceae Anderson & Anderson (1985) (Glossopteridaceae (Trapl (1926)) Zimmermann (1930), nom rej.]
  • Class †Cycadeoideopsida Scott (1923) [Cycadeoideophyta Taylor (1981); Cycadeoideidae Němejc (1968); Bennettitopsida Engler (1897); Bennettitophyta Kravtsov & Poljarnaja (1995); Bennettitidae Davitashvili (1949); Cycadoidea]
    • Order †Fredlindiales Anderson & Anderson (2003)
      • Family †Fredlindiaceae Anderson & Anderson (2003)
    • Order †Cycadeoideales Berry (1920) [Bennettitales (Engler (1892)) Schaffn.; Cycadeoideineae Němejc (1968); Williamsoniales Berry (1920); Wielandiellineae Nemejc (1968)]
      • Family †Varderkloeftiaceae Anderson & Anderson
      • Family †Laurozamitiaceae Anderson & Anderson
      • Family †Benneticarpaceae Anderson & Anderson
      • Family †Westersheimiaceae Němejc (1968)
      • Family †Sturianthaceae Doweld (2001) [Sturiellaceae Němejc]
      • Family †Williamsoniaceae (Carruthers (1870)) Nathorst (1943)
      • Family †Williamsoniellaceae Nakai (1943) [Wielandiellaceae (Novak (1954)) Němejc (1968)]
      • Family †Cycadeoideaceae R. Br. ex Wieland (1908) [Bennettitaceae Engler (1892); Pterophyllaceae Nakai (1943)]
  • Class †Caytoniopsida Thomas ex Frenguelli (1946) [Caytoniophytina Doweld (2001); Caytonia]
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References
  1. Rothwell G. W.; Scheckler S. E.; Gillespie W. H. (1989). "Elkinsia gen. nov., a Late Devonian gymnosperm with cupulate ovules". Botanical Gazette. 150 (2): 170–189. doi:10.1086/337763.
  2. McLoughlin S.; Carpenter R.J.; Jordan G.J.; Hill R.S. (2008). "Seed ferns survived the end-Cretaceous mass extinction in Tasmania". American Journal of Botany. 95 (4): 465–471. doi:10.3732/ajb.95.4.465. PMID 21632371.
  3. Potonié, H. (1899). Lehrbuch der Pflanzenpaläontologie. Berlin.
  4. Oliver F. W.; Scott D. H. (1904). "On the structure of the Palaeozoic seed Lagenostoma Lomaxi, with a statement of the evidence upon which it is referred to Lyginodendron". Philosophical Transactions of the Royal Society of London, Series B. 197 (225–238): 193–247. doi:10.1098/rstb.1905.0008.
  5. Grand'Eury C (1904). "Sur les graines Neuropteridées". Comptes Rendus de l'Académie des Sciences de Paris. 140: 782–786.
  6. Kidston R (1904). "On the fructification of Neuropteris heterophylla, Brongniart". Philosophical Transactions of the Royal Society of London, Series B. 197 (225–238): 1–5. doi:10.1098/rstb.1905.0001.
  7. White D (1904). "The seeds of Aneimites". Smithsonian Institution, Miscellaneous Collection. 47: 322–331.
  8. Hilton, J. & Bateman, R. M. (2006), "Pteridosperms are the backbone of seed-plant phylogeny", Journal of the Torrey Botanical Society, 33: 119–168, doi:10.3159/1095-5674(2006)133[119:PATBOS]2.0.CO;2
  9. Novíkov & Barabaš-Krasni (2015). Modern plant systematics. Liga-Pres. p. 685. doi:10.13140/RG.2.1.4745.6164. ISBN 978-966-397-276-3.
  10. Anderson, Anderson & Cleal (2007). Brief history of the gymnosperms: classification, biodiversity, phytogeography and ecology. Strelitzia. 20. SANBI. p. 280. ISBN 978-1-919976-39-6.
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