Pteridospermatophyta

Pteridospermatophyta Temporal range: Carboniferous-Cretaceous (Possible Eocene survival)
Fossil seed fern leaves from the Late Carboniferous of northeastern Ohio.
Scientific classification
Clade:	Polysporangiophytes
Clade:	Tracheophytes
Clade:	Spermatophytes
Division:	†Pteridospermatophyta
Orders
Calamopityales Callistophytales Caytoniales Gigantopteridales Glossopteridales Lyginopteridales Medullosales Peltaspermales

The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") refers to several distinct 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]

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.

Taxonomy

• 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]
  • Order †Caytoniales Gothan 1932
    • Family †Caytoniaceae (Thomas 1925) Kräusel 1926

References

External links

• Seed fern paleontology
• Seed ferns