The first trees appeared in the Middle - Late Devonian. One of the oldest fossil forests was found in the famous Gilboa locality (Givetian). The Late Devonian Archaeopteris has fronds with fan-shaped leaflets and is a well-known example of an early tree. This latter form belongs to the group of the Progymnosperms. The silicified wood of Archaeopteris is known as Callixylon. Callixylontrunks may reach a considerable diameter.

Taxon / Subject
Web Source
Gilboa Forest  Prof. Robert Titus, Hartwick College  
Progymnosperms Univ. California Mus. Paleontology, Berkeley  
Tetraxylopteris schmidtii Virtual Paleobotany Laboratory  
The genus Archaeopteris was originally established for Devonian foliage with fan-shaped pinnules. Archaeopteris is very widespread and has been reported from North and South America, Europe and  Aisa; several localities have yielded very large frond portions, e.g., Bear Island (Arctic), Kiltorckan (Ireland). The leaves bear macro- and microsporangia which are roughly of the same size and shape. The foliage has been correlated with the petrified wood Callixylon and the name Archaeopteris is also used for the reconstructed plant. 
Archaeopteris Univ. California Mus. Paleontology, Berkeley  
Archaeopteris Kathleen Pigg's "Plant Fossils and Evolution" Sterile and fertile leaves
Archaeopteris Paleontologisk Museum, Oslo  
Archaeopteris Media del Gekko  
Archaeopteris ABC News - Science Same pictures as above
Archaeopteris Botanik-online  
Archaeopteris The Forestry Source News item - mainly text
Archaeopteris gaspensis Virtual Paleobotany Laboratory  
Archaeopteris halliana Senckenberg, Frankfurt am Main Illustration on a stamp !
Archaeopteris halliana Parcs Canada  
Archaeopteris hibernica The Cork Geology Museum (Ireland)  
Archaeopteris hibernica Palaeobotany, Royal Holloway University London  
Callixylon is the wood of the Archaeopteris tree
Callixylon Virtual Paleobotany Laboratory radial section
Callixylon Virtual Paleobotany Laboratory tangential section
Callixylon Virtual Paleobotany Laboratory permineralized trunk
Callixylon Plant fossils of Kentucky, KGS  
Callixylon East Central University, Ada, OK  
Callixylon Univ. California Mus. Paleontology, Berkeley  same picture as above, in reverse!
  =  excellent !   =  very good
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  =  poor / no information

The last check of the list of links was done on 25 November 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; if applicable te general information on the main pages has been considered.
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
November 2002