PALAEOBOTANICAL RESEARCH GROUP

UNIVERSITY  MÜNSTER


 HISTORY  OF PALAEOZOIC  FORESTS
THE  EARLIEST LAND PLANTS


The earliest vascular land plants appeared about 425 million years ago in the late Early  Silurian.  This form, Cooksonia, consisted of small naked, dichotomously bifurcting axes bearing terminal sporangia. These plants were only a few centimeters high. Baragwanathia is a much more robust plant consisting of up to 30 cm long axes with spirally arranged leaves and it has been described from the Upper Silurian of Australia; unfortunately, the quality of the compressions is rather poor and no organic material is preserved.

The Early Devonian is characterized by a very strong radiation of land plants.  Four  major groups can be distinguished: the Rhyniophytes, the Zosterophyllophytes, the Lycopods and the Trimerophytes.  The Rhyniophytes are definitely among the best known land plants.  These ca. 15-20 cm high plants consist of naked, dichotomously branching axes terminally bearing fusiform sporangia.  Rhyniophytes lacked true roots but had single-celled rhizoids for taking up water and nutrients.  The silicified material from the Rhynie chert shows many anatomical details.  The equally sized Zosterophyllophytes are characterized by having dichotomously branching axes bearing laterally inserted sporangia; sporangia may be standing in strobili. Some Zosterophylls had small spine-like enations.  The Trimerophytes have a more complex vascular system and terminally positioned sporangia standing in dense clusters.  Some trimerophytes had monopodial main axes; however, lateral axes still had dichotomous branching.  Some Trimerophytes could reach a considerable height; Pertica from the late Early Devionan may already have attained a height of ca. 3 metres.  The Zosterophyllophytes are considered to be the ancestral group that gave rise to the Lycopods, whereas all other groups of land plants are regarded to have been evolved from the Trimerophytes.  The exquisit preservation of the Rhynie chert material enabled the recognition of the gametophyte stages of some of the earliest land plants.  Gametophytes have also been recognized in compression preservation.


Taxon / Subject
Web Source
Comments
Pics
Info
The oldest land plants 1 Hans Steur's Paleobotany Pages   
The oldest land plants 2 Hans Steur's Paleobotany Pages   
Pre-Devonian vascular land plants: Baragwanathia andCooksonia
Baragwanathia is a putatitive early lcopod from the Silurian of southern Australia. The age of these fossils was long controversial, but now it is agreed that they are Silurian.
Baragwanathia Museum Victoria  
Baragwanathia Virtual Paleobotany Laboratory  
Baragwanathia Astrobiology UCLA  
Cooksonia
Cooksonia hemisphaerica Virtual Paleobotany Laboratory  
Cooksonia Virtual Paleobotany Laboratory  
Cooksonia Charles Wellman, Sheffield University SEM picture
Cooksonia pertonii Hans Steur's Paleobotany Pages   
Cooksonia pertonii Hans Steur's Paleobotany Pages  
One of the most famous Early Devonian land plant localities is Rhynie in Aberdeenshire, Scotland. The Rhynie Chert is one of the most important fossil plant occurrences because it represents the oldest and most completely preserved terrestrial ecosystem. The Rhynie Chert has been radiometrically dated at 396 Ma (Pragian). Plants remains show excellent cellular preservation. Three groups of plants are represented: the Rhyniophytes, the Zosterphyllophytes and a lycopod. Although plants are preserved in great detail natural affinities of the taxa are not always clear. 
Rhynie Chert Paläobotanik Münster  
have a look!
Rhynie Chert Rhynie Chert Reserach Group, Aberdeen The ultimate Rhynie Chert Site !!
Rhynie Chert Virtual Paleobotany Laboratory  
The Rhyniophytes are a group of early land plants originally described from the Rhynie Chert. They have naked, dichotomously branching axes with terminally positioned sporangia.  The systematic position of Aglaophyton, Horneophyton and Nothia is not clear, because of differences in the vascular system respectively sporangium morphology; the latter form also shows resemblances with Zosterophyllophytes.  Some authors classify these taxa in separate groups.  Several forms have been interpreted as compression counterparts of the Rhyniophytes; however, this needs further clearification.
Rhynia gwynne-vaughanii
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages   
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages Reconstruction and overview
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages Cross sections
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages Epidermis and stoma
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages Hemispherical projection on axis
Rhynia gwynne-vaughanii Hans Steur's Paleobotany Pages Decaying axes
Rhynia gwynne-vaughanii Paläobotanik Münster  
have a look!
Rhynia gwynne-vaughanii Ohio State University, Lima   
Rhynia gwynne-vaughanii Rhynie Chert Reserach Group, Aberdeen Text with several pictures
Aglaophyton major and the male gametophyte Lyonophyton
Aglaophyton major Paläobotanik Münster Germinating spore / gametophyte 
have a look !
Aglaophyton major Virtual Paleobotany Laboratory  
Aglaophyton major Hans Steur's Paleobotany Pages Reconstruction and overviews
Aglaophyton major Paläobotanik Münster  
have a look!
Aglaophyton major Paläobotanik Münster Stoma
have a look!
Aglaophyton major Rhynie Chert Reserach Group, Aberdeen Text with several pictures
Horneophyton lignieri
Horneophyton lignieri Virtual Paleobotany Laboratory Sporangia
Horneophyton lignieri Hans Steur's Paleobotany Pages  Conducting strand and spores
Horneophyton lignieri Hans Steur's Paleobotany Pages Rhizomes with rhizoids
Horneophyton lignieri Hans Steur's Paleobotany Pages  Sporangium
Horneophyton lignieri Hans Steur's Paleobotany Pages  Spores
Horneophyton lignieri Rhynie Chert Reserach Group, Aberdeen Text with several pictures
Nothia
Nothia aphylla Hans Steur's Paleobotany Pages Reconstruction and overview
Nothia aphylla Rhynie Chert Reserach Group, Aberdeen Text with several pictures
The Zosterophyllophytes are a group of Early to Middle Devonian plants with mostly dicotomously branching axes and laterally inserted, usually more or less kidney-shaped sporangia.  Several Zosterphylls have naked axes, others have small spine-like enations.  Very typical are H-shaped branching patterns and coiled axis apices.  Most forms are known as compressions, however also anatomically preserved material is known.
Zosterophylls Univ. California Mus. Paleontology, Berkeley  
Crenaticaulis
Crenaticaulis Virtual Paleobotany Laboratory  
Sawdonia
Sawdonia acanthotheca Virtual Paleobotany Laboratory  
Sawdonia ornata Hans Steur's Paleobotany Pages    
Sawdonia ornata Hans Steur's Paleobotany Pages    
Serrulacaulis
Serrulacaulis furcatus Virtual Paleobotany Laboratory  
Rebuchia
Rebuchia ovata Smithsonian, Washington DC   
Trichopherophyton
Trichopherophyton Rhynie Chert Reserach Group, Aberdeen The first zosterphyll from the Rhynie Chert
Ventarura
Ventarura Rhynie Chert Reserach Group, Aberdeen Another zosterphyll from Rhynie
Zosterophyllum
Zosterophyllum divaricatum Virtual Paleobotany Laboratory  
Zosterophyllum rhenanum Institut für Spezielle Botanik, Jena Alternation of generations
The Trimerophytes are a group Early and Middle Devonian plants with either dichotomously branching axes, or with a monopodial main axes.  The Trimerophytes were certainly the most robust plants occurring during the Early Devonian.
Trimerophytes Univ. California Mus. Paleontology, Berkeley  
Psilophyton
Psilophyton ornata Virtual Paleobotany Laboratory  
Psilophyton Univ. California Mus. Paleontology, Berkeley  
Psilophyton crenulatum M.J. Farabee: Online Biology Book   
Pertica
Pertica quadrifaria Geological  Survey Maine State fossil of Maine
Pertica quadrifaria Geological  Survey Maine State fossil of Maine
Pertica Univ. California Mus. Paleontology, Berkeley   
Pertica Virtual Paleobotany Laboratory    
Early Lycopodiophytes
Asteroxylon
Asteroxylon Virtual Paleobotany Laboratory    
Asteroxylon mackiei Hans Steur's Paleobotany Pages  Reconstruction and overview
Asteroxylon mackiei Hans Steur's Paleobotany Pages  Star-shaped xylem
Asteroxylon mackiei Hans Steur's Paleobotany Pages  Tracheids
Asteroxylon mackiei Hans Steur's Paleobotany Pages  Leaves
Asteroxylon mackiei Astrobiology UCLA Reconstruction
Asteroxylon mackiei Rhynie Chert Reserach Group, Aberdeen Text with several pictures
 
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Disclaimer

The last check of the list of links was done on 27 December 2003. 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; if applicable te general information on the main pages has been condered.
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 links may be outdated.  Suggestions for improvement and hints to other internet resources are most welcome


© Forschungsstelle für Paläobotanik, Westfälische Wilhelms-Universität Münster
December 2003