PALAEOBOTANICAL RESEARCH   GROUP   UNIVERSITY  MÜNSTER

Pteridosperms or seed ferns are a very heterogeneous group of extinct plants with mostly fern-like foliage but with real seeds.  They are mostly reconstructed as small trees but also forms with a climbing growth habit gave been found.  Some forms, nobbly Medullosales,  have really large fronds which could be up to 7 m long.  Several groups can be distinguished within the pteridosperms.  The classification of seed ferns is primarily based on fructifications and/or anatomical features. Eight groups of pteridosperms are presently recognised, six of them are known from the Palaeozoic and three from the Mesozoic.  Some groups are very well known including their reproductive organs, whereas others are still very poorly understood and based on anatomically preserved vegetative remains, mostly axes.

Pteridosperms evolved in the latest Devonian (Fammenian) and became more common in the Carboniferous. The Lyginopteridales are most common in the Namurian and Lower Westphalian. The Medullosales took over the leading role during the Westphalian became less common in the latest Stephanian and persisted into the Permian. The small group of the Callistophytales is known from the Upper Westphalian to Lower Permian. Peltaspermales evolved in the late Stephanian and were most common in the Triassic. The essentially Permian Glossopteridales are typical Gondwana elements. Corystospermales and Caytoniales are Mesozoic pteridosperms.

Taxon / Subject	Web Source	Comments	Pics	Info
The Lyginopteridales are one of the best known groups of pteridosperms, of which permineralized axes (e.g. Lyginopteris), rather small cupulate seeds (e.g. Lagenostoma) and pollen organs have been described; compression fossils of pollen organs have been described as Crossotheca.  Lyginopteridales are commonly reconstructed as small slender trees.  The foliage with its typically bifurcated fronds is of the sphenopteroid type.
Lyginopteris and Lagenostoma	R.A. Spicer, The Open University, Milton Keynes	permineralized axis and seed
Sphenopteris crepinii	Collection Jens-Wilhelm Janzen	foliage and pollen organs
The Medullosales are one of the most widespread groups Palaeozoic seed ferns. They have rather large seeds which can be several cm long; one of the seed types is Trigonocarpus. Anatomically preserved seeds have been described as Pachytesta. The pollen organs are relatively complex, usually consisting of a (large) number of fused pollen sacs; one of the pollen organs has been described as Bernaultia. Fronds are typically bifurcated.  Foliage form-genera like Neuropteris and Alethopteris are commonly attributed to the Medullosales. Medullosales had different growth forms, varying from medium-sized tree fern-like plants with very large fronds to liana-like plants with rather small compact fronds.
Pachytesta sp.	Palaeobotany Münster	coal ball material	have a look !
Trigonocarpus sp	Univ. California Museum of Paleontology, Berkeley
Trigonocarpus	Collection Jens-Wilhelm Janzen
Bernaultia formosa	Palaeobotany Münster	coal ball material	have a look !
Pteridosperm foliage is often difficult to distinguish from fern foliage.  In fact, the natural affinity of many Carboniferous foliage types is still unknown.  Foliage is therefore classified in so-called form-genera; such form-genera of foliage types of unknown natural affinity (ferns + pteridosperms) are usually listed under pteridophylla.  Form-genera are defined on the basis of pinnule outline and venation pattern.  Most Carboniferous fern-like foliage appears to be seed fern foliage. Common foliage types are Neuropteris, Alethopteris and Sphenopteris.  Many of these foliage taxa are valuable index fossils.
Seed fern and fern foliage	Hans' (Steur) Paleobotany Pages	with identification table
Alethopteris is a form-genus for fern-like foliage with tongue-shaped, decurrent pinnules. The venation is pinnate with a strong, usually sunken midvein; some additional smaller veins arise directly from the rachis (in the decurrent basal part of the pinnule).  Fonds are typically bifurcated and large to very large; however, most of the specimens found are rather small.  Alethopteris is commonly considered to be medullosan foliage.
Alethopteris decurrens	M. Hieb's Plant Fossils of West Virginia
Alethopteris decurrens	M. Hieb's Plant Fossils of West Virginia
Alethopteris lonchitica	M. Hieb's Plant Fossils of West Virginia	large specimen without much detail
Alethopteris sp.	M. Hieb's Plant Fossils of West Virginia
Alethopteris sp.	M. Hieb's Plant Fossils of West Virginia	this might be a Mariopteris
Alethopteris sp.	Mazon Creek Exhibit, Illinois State Museum
Alethopteris sp.	University of Oklahoma
Alethopteris sp.	M. Hieb's Plant Fossils of West Virginia
Alethopteris sp. and Neuropteris sp.	Plant Fossils of Kentucky, Kentucky Geological Survey
Alethopteris	Collection Jens-Wilhelm Janzen	incl. a very large specimen
Neuropteris is another common foliage type. It is characterized by it tongue-shaped pedicellate pinnules which have a pinnate venation. Neuropteris fronds are usually bifurcated and large to very large. Neuropteris is also commonly considered to be medullosan foliage.
Neuropteris sp.	Mazon Creek Exhibit, Illinois State Museum
Neuropteris obliqua	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp.	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp.	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp.	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp.	M. Hieb's Plant Fossils of West Virginia
Neuropteris sp.	M. Hieb's Plant Fossils of West Virginia	basal bifurcation of the frond
Neuropteris	Collection Jens-Wilhelm Janzen	almost complete bifurcated frond
Neuropteris	Natural History Museum, Maastricht, The Netherlands
Neuropteris	Hans' (Steur) Paleobotany Pages	page with additional picture
Paripteris	Collection Jens-Wilhelm Janzen	a segregrate of Neuropteris
Sphenopteris and Eusphenopteris are two form-genera for foliage types with (strongly) dissected or lobed pinnules. Euspenopteris has pinnules with rounded lobes, whereas Sphenopteris sensu stricto has more dissected lobes. Eusphenopterid fronds are considered to be pteridosperm foliage. However, Sphenopteris is a form-genus that is known to include seed ferns and true ferns. Lyginopteridales have bifurcted fronds with sphenopterid pinnules.
Eusphenopteris sp.	Paläobotanik, Münster		have a look !
Eusphenopteris sp.	M. Hieb's Plant Fossils of West Virginia
Eusphenopteris sp.	M. Hieb's Plant Fossils of West Virginia
Eusphenopteris sp.	M. Hieb's Plant Fossils of West Virginia
Eusphenopteris	Collection Jens-Wilhelm Janzen
Diplothmema sp.	Mazon Creek Exhibit, Illinois State Museum	another type of sphenopterid foliage
Mariopteris is a form genus for relatively small compact fronds which are bifurcated twice. The pinnules are tongue-shaped to assymmetrically triangular in outline with a distinct basal lobe (at least the pinnules closest to the main axes). Although it is clear that most mariopterids are seed ferns, their natural affinity remains unclear. Mariopterids obviously had a climbing growth habit.
Mariopteris muricata	M. Hieb's Plant Fossils of West Virginia
Mariopteris sp.	M. Hieb's Plant Fossils of West Virginia
Mariopteris sp.	M. Hieb's Plant Fossils of West Virginia
Mariopteris	Collection Jens-Wilhelm Janzen	including a complete frond
Karinopteris	Paläobotanik, Münster	climber hook of a mariopterid	have a look !
Reticulopteris is a small genus including fronds with pinnules having a neuropterid shape but differing in having a reticulate venation pattern
Reticulopteris	Collection Jens-Wilhelm Janzen
Cyclopteris is a form-genus for large circular pinnules, up to ca. 10 cm in diameter, which are found in the basal parts of Neuropteris fronds or in the basal parts of its pinnae.
Cyclopteris	Collection Jens-Wilhelm Janzen
In contrast to true ferns Pteridosperms have well developed, very resistant cuticles. Each genus, or in most cases even every species, has its own typical epidermal pattern reflected in the overlying cuticle. Cuticles are therefore very useful in taxonomic. Moreover, cuticles also display a number of other features that can be used in palaeoecological and palaeoclimatological studies.
Lescuropteris genuina and   Alethopteris zeilleri cuticles	Palaeobotany Münster		have a look !

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