PALAEOBOTANICAL RESEARCH GROUP
UNIVERSITY  MÜNSTER

HISTORY  OF  PALAEOZOIC  FORESTS
PTERIDOSPERMS  OR  SEED   FERNS


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, notably 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
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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.
Sphenopteris crepinii Collection Jens-Wilhelm Janzen foliage and pollen organs
Sphenopteris Kentucky Paleontological Society foliage
Eusphenopteris M. Hieb's Plant Fossils of West Virginia  
Diplotmema Univ. Pierre et Marie Curie, Paris left image
Lyginopteris M. Hieb's Plant Fossils of West Virginia foliage
Sphenopteris artemisaefolioides Humboldt State University  
Sphenopteris artemisaefolioides Humboldt State University  
Sphenopteris hollandica Senckenberg image on stamp    
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. They produced large prepollen grains, e.g., Schopfipollenites. Fronds are typically bifurcated.  Whittleseya is another type of pollen organ.  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 !
Pachytesta Virtual Paleobotany, UCL Berkeley  
Trigonocarpus sp Univ. California Mus. Paleontology, Berkeley  
Trigonocarpus Collection Jens-Wilhelm Janzen  
Trigonocarpus Virtual Paleobotany, UCL Berkeley link not active ?    
Bernaultia formosa Virtual Paleobotany, UCL Berkeley listed as Dolerotheca
Bernaultia formosa Palaeobotany Münster coal ball material
have a look !
Whittleseya microphylla Virtual Paleobotany, UCL Berkeley compression
Medullosa noei Virtual Paleobotany, UCL Berkeley permineralized stem
Myeloxyleon Virtual Paleobotany, UCL Berkeley permineralized frond petiole 
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 decurrens M. Hieb's Plant Fossils of West Virginia a magnificent specimen 
Alethopteris decurrens SOES Geology Collection  
Alethopteris lonchitica M. Hieb's Plant Fossils of West Virginia large specimen without much detail
Alethopteris lonchitica M. Hieb's Plant Fossils of West Virginia top of pinna
Alethopteris serlii Humboldt State University  
Alethopteris sullivantii Virtual Paleobotany, UCL Berkeley  
Alethopteris Fossils of Nova Scotia  
Alethopteris Humboldt State University listed as Pecopteris
Alethopteris sp. M. Hieb's Plant Fossils of West Virginia with seeds
Alethopteris sp. M. Hieb's Plant Fossils of West Virginia  
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. M. Hieb's Plant Fossils of West Virginia  
Alethopteris sp. Mazon Creek Exhibit, Illinois State Museum  
Alethopteris SOES Geology Collection  
Alethopteris SOES Geology Collection  
Alethopteris sp. M. Hieb's Plant Fossils of West Virginia  
Alethopteris Virtual Paleobotany, UCL Berkeley  
Alethopteris Leeds Geological Association  
Alethopteris sp. and Neuropteris sp. Plant Fossils of Kentucky  
Alethopteris Collection Jens-Wilhelm Janzen incl. a very large specimen
Alethopteris Senckenberg image on stamp    
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 heterophylla M. Hieb's Plant Fossils of West Virginia  
Neuropteris parvifolia Geol. Dienst NRW Krefeld  
Neuropteris scheuchzeri Southern Illinois Univ. 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 M. Hieb's Plant Fossils of West Virginia  
Neuropteris Collection Jens-Wilhelm Janzen almost complete bifurcated frond
Neuropteris gigantea Natural History Museum, Maastricht, NL  
Neuropteris Hans' (Steur) Paleobotany Pages page with additional picture
Neuropteris Humboldt State University  
Neuropteris Virtual Paleobotany, UCL Berkeley  
Neuropteris Kentucky Paleontological Society  
Neuropteris Univ. California Museum Berkeley  
Neuropteris SOES Fossil Collection  
Neuropteris SOES Fossil Collection  
Paripteris Collection Jens-Wilhelm Janzen a segregrate of Neuropteris
Linopteris neuropteroides Geol. Dienst NRW Krefeld  
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 sp. M. Hieb's Plant Fossils of West Virginia   
Eusphenopteris Collection Jens-Wilhelm Janzen  
Diplothmema sp. Mazon Creek Exhibit, Illinois State Mus. another type of sphenopterid foliage
Sphenopteris M. Hieb's Plant Fossils of West Virginia  
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 nervosa Geol. Dienst NRW Krefeld  
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 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 !
In addition to the taxa listed above there are several other (groups of) pteridosperms. In the Euramerian Upper  Carboniferous and Lower Permian these include the Callistophytales and Peltaspermales.
Dickonites pluckenetii Geotechnik TU Dresden Callistophytalean foliage
 
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Disclaimer

The last check of the list of links was done on 6 December 2002.  The links give the most direct connections to pictures available on the web; in many cases they are from sites that have additional palaeobotanical information.  The above ratings refer to: 
1. Pics: the quality of the specimens, particularly with regard to characteristic features, and to the quality of the pictures. 
2. Info: the additional information provided.
Ratings are of course subjective but should be helpful for finding the fastest way to good pictures on the web. Own pictures are of course not rated. This is up to you! 
Although links are checked regularly, some may be outdated.  Suggestions for improvement and hints to other internet resources are most welcome

 

© Forschungsstelle für Paläobotanik, Westfälische Wilhelms-Universität Münster
December  2002