The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a

polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...

group of extinct seed-bearing plants (

spermatophyte A spermatophyte (; ), also known as phanerogam (taxon Phanerogamae) or phaenogam (taxon Phaenogamae), is any plant that produces seeds, hence the alternative name seed plant. Spermatophytes are a subset of the embryophytes or land plants. They inc ...

s). The earliest fossil evidence for plants of this type is the genus ''Elkinsia'' of the late

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wh ...

age. They flourished particularly during the

Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carboniferou ...

and

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleo ...

periods. Pteridosperms declined during the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...

Era and had mostly disappeared by the end of the

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Period, though some pteridosperm-like plants seem to have survived into

Eocene The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...

times, based on

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

finds in

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

. With regard to the enduring utility of this

division Division or divider may refer to: Mathematics *Division (mathematics), the inverse of multiplication *Division algorithm, a method for computing the result of mathematical division Military *Division (military), a formation typically consisting ...

, many palaeobotanists still use the pteridosperm grouping in an informal sense to refer to the seed plants that are not

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. The term "angiosperm" is derived from the Greek words ('container, vessel') and ('seed'), and refers to those plants ...

s, coniferoids (

conifer Conifers are a group of cone-bearing seed plants, a subset of gymnosperms. Scientifically, they make up the division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a single extant class, Pinopsida. All ext ...

s or

cordaite ''Cordaites'' is an important genus of extinct gymnosperms which grew on wet ground similar to the Everglades in Florida. Brackish water mussels and crustacea are found frequently between the roots of these trees. The fossils are found in rock s ...

s), ginkgophytes or

cycad Cycads are seed plants that typically have a stout and woody (ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male o ...

ophytes (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.

History of classification

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 Cycads are seed plants that typically have a stout and woody ( ligneous) trunk with a crown of large, hard, stiff, evergreen and (usually) pinnate leaves. The species are dioecious, that is, individual plants of a species are either male or ...

. 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

fern A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes exce ...

s and cycads. Shortly afterwards, the British palaeobotanists

Frank Oliver Frank Oliver may refer to: * Frank Oliver (American football) (born 1952), American football player * Frank Oliver (footballer) (1882–?), English footballer *Frank Oliver (politician) (1853–1933), Canadian politician *Frank Oliver (rugby union) ...

and

Dukinfield Henry Scott Dr Dukinfield Henry Scott FRS HFRSE LLD (28 November 1854 – 29 January 1934) was a British botanist. Biography Scott was born in London on 28 November 1854, the fifth and youngest son of architect Sir George Gilbert Scott and his wife Caro ...

(with the assistance of Oliver's student at the time,

Marie Stopes Marie Charlotte Carmichael Stopes (15 October 1880 – 2 October 1958) was a British author, palaeobotanist and campaigner for eugenics and women's rights. She made significant contributions to plant palaeontology and coal classificati ...

) 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. Soon, additional evidence came to light suggesting that seeds were also attached to the Carboniferous fern-like fronds ''Dicksonites'', '' Neuropteris'' and ''Aneimites''. Initially it was still thought that they were "

transitional fossil A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. This is especially important where the descendant group is sharply differentiated by gross a ...

s" 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 The Lyginopteridales were the archetypal pteridosperms: They were the first plant fossils to be described as pteridosperms and, thus, the group on which the concept of pteridosperms was first developed;Oliver, F. W. & Scott, D. H. (1904). "On t ...

Medullosales The Medullosales is an extinct order of pteridospermous seed plants characterised by large ovules with circular cross-section and a vascularised nucellus, complex pollen-organs, stems and rachides with a dissected stele, and frond-like leaves. ...

Callistophytales The Callistophytales was an order of mainly scrambling and lianescent plants found in the wetland "coal swamps" of Euramerica and Cathaysia. They were characterised by having bilaterally-symmetrical, non-cupulate ovules attached to the underside ...

and

Peltaspermales The Peltaspermales are an extinct order of plants belonging to Pteridospermatophyta The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants (spermatophytes). The earlies ...

. 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 Corystospermaceae is a natural family of seed ferns (Pteridospermatophyta) also called Umkomasiaceae, and first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. Corystosperm ...

. Some palaeobotanists also included seed plant groups with entire leaves such as the

Glossopteridales Glossopteridales is an extinct order of plants belonging to Pteridospermatophyta, or seed ferns, also known as Arberiales and Ottokariales. They arose at the beginning of the Permian () on the southern continent of Gondwana, but became extinct a ...

and Gigantopteridales, which was stretching the concept. In the context of modern phylogenetic models, 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 In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

'grade-group' with no common lineage. One of the few characters that may unify the group is that the

ovule In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the '' integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the ...

s were borne in a

cupule A cupule is a small structure shaped like a cup, including: * In archeology, rock cupules are circular man-made hollows on the surface of a large rock or a rock slab ** On a smaller artifact they are called a cupstone. * In botany: the base of an ...

, a group of enclosing branches, but this has not been confirmed for all "pteridosperm" groups.

Phylogeny

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

Taxonomy

Specimen at Natural History Museum, Gothenburg 02 (cropped)

* Family ?† Nystroemiaceae Wang & Pfefferkorn 2009 * Order ?† Alexiales Anderson & Anderson (2003) ** Family † Alexiaceae Anderson & Anderson (2003) * Order ?†

Calamopityales The Calamopityales are an extinct order of plants belonging to Pteridospermatophyta The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants ( spermatophytes). The earlie ...

Němejc (1963) uteoxylales Taylor & Taylor (1992)** Family † Calamopityaceae (Solm. (1896)) Scott (1909) uteoxylaceae Barnard & Long (1973); Stenomyelaceae Scott (1923)* Order ?† Erdtmanithecales Friis and Pedersen (1996) ** Family † Erdtmanithecaceae Friis and Pedersen (1996) * Order ?† Hlatimbiales Anderson & Anderson (2003) ** Family † Hlatimbiaceae Anderson & Anderson (2003) * Order † Umkomasiales Doweld (2001) orystospermales; Ptilozamitales (Němejc 1950)** Family † Angaropeltidaceae Doweld (2001) ardiolepidaceae Meyen 1977** Family † Umkomasiaceae Petriella (1981) (

(Thomas (1933)) Stockey & Rothwel nom. illeg.; Zuberiaceae Němejc (1968); Pachypteridaceae de Zigno; Ptilozamitaceae Němejc (1950)] * Class ?† Arberiopsida Doweld (2001) lealopsida; Dicranophyllopsida Němejc 1968** Order † Dicranophyllales Meyen (1984) emend. Anderson, Anderson & Cleal (2007) *** Family † Dicranophyllaceae Němejc (1959) ex Archangelsky & Cúneo (1990) ** Order † Aberiales Meyen (1978) ex Meyen (1984) *** Family † Schmeissneriaceae Zhou (1997) *** Family † Arberiaceae (Rigby (1972) Anderson & Anderson (1985) * Class † Moresnetiopsida Doweld (2001) oresnetiophyta Doweld (2001); Elkinsiophytina** 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) lkinsiales Rothwell, Scheckler & Gillespie (1989); Hydraspermatales Krassilov (1989)*** Family † Eurystomataceae Long (1975) *** Family † Eospermatacesidae Long (1975) *** Family † Moresnetiaceae Němejc (1963) emend. Anderson, Anderson & Cleal (2007) enomospermaceae Long (1975); Elkinsiaceae Rothwell, Scheckler & Gillespie (1989) ex Cleal; Hydraspermaceae* Class †

Lyginopteridopsida The Lyginopteridales were the archetypal pteridosperms: They were the first plant fossils to be described as pteridosperms and, thus, the group on which the concept of pteridosperms was first developed;Oliver, F. W. & Scott, D. H. (1904). "On th ...

Novák (1961) emend. Anderson, Anderson & Cleal (2007) agenostomatopsida Cleal (1993); Lyginopteridophyta Doweld (2001); Lyginopteridophytina** Order ?† Hexapterospermales Doweld (2001) *** Family † Colpospermaceae Doweld (2001) *** Family † Hexapterospermaceae Doweld (2001) nom cons. otonieaceae (Halle (1933)) Remy & Remy (1959) emend. Anderson & Anderson (2007)** Order †

(Corsin (1960)) Havlena (1961) agenostomatales 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)] * 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) (

Corsin (1960); Trigonocarpales Seward 1917 nom. inv.; Neuropteridales Schimper (1869); Rhexoxylales] *** Family † Potonieaceae Halle (1933) emend. Anderson, Anderson & Cleal (2007) achivestitaceae; Perispermaceae*** Family † Polylophospermaceae Doweld (2001) emend. Anderson, Anderson & Cleal (2007) *** Family † Stephanospermaceae Doweld (2001) emend. Anderson, Anderson & Cleal (2007) *** Family † Trigonocarpaceae Göppert (1842) *** Family † Neuropteridaceae Laveine (1966) ncl. Odontopteridaceae Trapl (1926) sensu Corsin (1960); Neurodontopteridaceae Laveine (1966)*** Family † Pachytestaceae Doweld (2001) ( Medullosaceae (Gopp. (1842)) Sterzel (1896); Whittleseyaceae Remy & Remy (1959); Protoblechnaceae Wagner (1967); Neuralethospermaceae Laveine (1967)) *** Family † Callipteridaceae Corsin ex Wagner (1965) allipteridiaceae; Callipteraceae*** Family † Alethopteridaceae (Lesquereux (1884)) Corsin (1960) emend. Anderson, Anderson & Cleal (2007) *** Family † Cyclopteridaceae Corsin ex Wagner (1964) * Class † Callistophytopsida allistophytina** Order †

Rothwell (1981) emend. Anderson, Anderson & Cleal (2007) oroxylales Němejc (1968) *** Family † Cornucarpaceae Doweld (2001) remopteridaceae*** Family †

Callistophytaceae The Callistophytaceae was a family of seed ferns (pteridosperms) from the Carboniferous and Permian periods. They first appeared in late Middle Pennsylvanian (Moscovian) times, 306.5–311.7 million years ago ( Ma) in the tropical coal forests o ...

Stidd & Hall (1970), nom. cons. ariopteridaceae Němejc (1968); Callospermariaceae Long (1975)* Class † Peltaspermopsida Doweld (2001) eltaspermidae Němejc (1968); Psygmophyllopsida Koidzumi (1939)** Order † Sporophyllitales Doweld (2001) *** Family † Sporophyllitaceae Doweld (2001) *** Family † Leuthardtiaceae Doweld (2001) ** Order † Trichopityales Doweld (2001) sygmophyllales Nakai (1943)*** Family † Psygmophyllaceae Zalessky (1937) emend. Naugolnykh *** Family † Syniopteridaceae Petrescu & Dragastan (1981) *** Family † Trichopityaceae Němejc (1968) lorin emend./small> ** Order †

Taylor (1981) epidopteridales Němejc (1968)*** Family † Autuniaceae Doweld (2001) *** Family †

Peltaspermaceae Peltaspermaceae is a natural family of seed ferns (Pteridospermatophyta) widespread in both northern and southern hemispheres coal measures of Permian and Triassic age. Peltasperms persisted in a relictual distribution in Patagonia during the Ea ...

(Thomas (1933)) Pilger & Melchoir (1954)) [Compsopteridaceae Petrescu & Dragastan (1981); Cycadopteridaceae Laguzen (1887); Thinnfeldiaceae Zimmerman (1959); Lepidopteridaceae Němejc (1968)] *** Family †Vetlugospermaceae Naugolnykh (2012) * Class †Phasmatocycadopsida Doweld (2001) ** Order †Phasmatocycadales Doweld (2001) aeniopteridales*** Family † Phasmatocycadaceae Doweld (2001) permopteridaceae Doweld (2001)** Order † Gigantopteridales Li & Yao (1983) igantonomiales Meyen (1987)*** Family †

Emplectopteridaceae The Emplectopteridaceae were pteridosperms known mainly from Permian floras of the Cathaysian Realm. They were mostly shrubby plants with a scrambling or upright habit, and favoured a range of habitats from arid to moist or even aquatic.Wang Zi ...

Wagner (1967) *** Family † Gigantopteridaceae Koidzumi (1936) ardioglossaceae Koidzumi ex Jongmans (1958); Gigantonomiaceae Meyen (1987)* Class † Pentoxylopsida Pant ex Doweld (2001) entoxylophytina Lemoigne (1988); Pentoxyla** Order † Pentoxylales Pilger & Melchior (1954) *** Family † Lindthecaceae Anderson & Anderson (2003) *** Family † Pentoxylaceae Pilger & Melchior (1954) entoxyleae Sahni (1948)* Class † Dictyopteridiopsida Doweld (2001) ttokariopsida Anderson & Anderson (2007); Glossopteridopsida Plumstead (1956)** Family † Gangamopteridaceae Nicholson & Lydekker (1889) ** Order † Dictyopteridiales McLoughlin ex Doweld (2001) ttokariales Anderson & Anderson (1985)*** Family † Breyteniaceae Doweld (2001) *** Family † Dictyopteridiaceae Rigby (1978) ttokariaceae 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) (

Luber & Schwedov (1963), nom. rej.] *** Family † Rigbyaceae Anderson & Anderson (1985) (

Glossopteridaceae The Glossopteridaceae are an extinct family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the ...

(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) ennettitales (Engler (1892)) Schaffn.; Williamsoniales Berry (1920); Wielandiales Nemejc (1950) nom. nud. *** Family † Benneticarpaceae Anderson & Anderson *** Family † Laurozamitiaceae Anderson & Anderson *** Family † Macrotaeniopteridaceae Bock 1969 *** Family † Sturianthaceae Doweld (2001) turiellaceae Němejc*** Family † Varderkloeftiaceae Anderson & Anderson *** Family † Westersheimiaceae Němejc (1968) *** Family †

Williamsoniaceae ''Williamsoniaceae'' is a family within the Bennettitales, an extinct group of seed plants within the Cycadophyta subdivision. Members of this family are believed to have been around two meters tall and with widely serrate leaves along a central ...

(Carruthers (1870)) Nathorst (1943) *** Family † Williamsoniellaceae Nakai (1943) ielandiellaceae (Novak (1954)) Němejc (1968)*** Family † Cycadeoideaceae R. Br. ex Wieland (1908) ennettitaceae Engler (1892); Pterophyllaceae Nakai (1943)* Class † Caytoniopsida Thomas ex Frenguelli (1946) aytoniophytina Doweld (2001); Caytonia** Order †

Caytoniales The Caytoniales (Figs. 1-2) are an extinct order of seed plants known from fossils collected throughout the Mesozoic Era, around . They are regarded as seed ferns because they are seed-bearing plants with fern-like leaves. Although at one time c ...

Gothan (1932) *** Family † Caytoniaceae (Thomas (1925)) Kräusel (1926) * Class † Axelrodiopsida Anderson & Anderson ** Order † Axelrodiales Anderson & Anderson (2007) *** Family † Zamiostrobacea Anderson & Anderson (2007) *** Family † Axelrodiaceae Anderson & Anderson (2007)

References

External links

Seed fern paleontology

{{Taxonbar, from=Q1130372 Plant divisions Prehistoric plants Devonian plants Carboniferous plants Permian plants Triassic plants Jurassic plants Cretaceous plants Paleocene plants Eocene plants Devonian first appearances Eocene extinctions Paraphyletic groups