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PALAEOBOTANICAL RESEARCH   GROUP
 
UNIVERSITY  MÜNSTER

 
HISTORY  OF  PALAEOZOIC  FORESTS
FOSSIL  AND  EXTANT  LYCOPHYTES


All modern clubmosses or lycopods are small herbaceous plants. Most of their late Palaeozoic, particularly their Carboniferous relatives were large trees. Several genera are known. One of the best tree-like lycopods is Lepidodendron. Sigillaria is another example of a lycopod tree. Genera are distinguished on the basis of the shape of the leaf cushions on the stems, their anatomy, their reproductive structures and their growth habit. During most of the Westphalian arborescent lycopods were the dominant elements in coal swamp floras and hence also the most important biomass producers. Up to 80% of  the North American and  European Westphalian coals can consist of biomass derived from arborescent lycopods. Tree-like lycopods were heterosporous; in some forms the megaspores with surrounding megasporangia and megasporophylls look almost seed-like. Unlike in any other type of tree which all have secondary growth concentrated in the xylem (wood), the secondary growth of arborescent lycopods mainly took place in the cortex (bark). Several examples of in situ preserved fossil lycopod forest are known. Most arborescent lycopods became extinct by the end of the Westphalian. Apart from arborescent forms also herbaceous lycopods are known. These include homosporous forms similar to most modern lycopods and heterosporous forms similar to the modern Selaginella. Some authors even assign Carboniferous forms to the extant genus Selaginella. If this would be true, this would be the longest living genus of higher land plants.



 
 
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Lycophytes Virtual Paleobotany Laboratory links to pictures and further info
One of the most common and most widespread Carboniferous tree lycopods is Lepidodendron. The genus was orginally described for stem surfaces showing the characteristic spirally arranged diamond-shaped, vertically positioned leaf cushions. Some Lepidodendron species could be up to ca. 40 m high. Most peculiar is their anatomy showing that the secondary growth mainly took place in the cortex; the proportion of xylem (wood) is relatively small. During their life the trees shed parts of their outer bark and basal parts of the trunks and larges stems typically show various stages of decortication. Lepidodendron trees rooted horizontally, indicating humid environments. Root systems are known as Stigmaria. Several types of branching patterns of aerial stems have been distinguished, on the basis of which the genus has been differentiated into several genera. Branching can be lateral or dichotomous; large branch scars of lateral branches have been described as Ulodendron. Leaves were long, narrow and stiff (Lepidophyllum); those of the the ultimate branches being smaller and needle-like. The plants were heterosporous and some of the strobili, known as Lepidostrobus, could reach a length of nearly 1 m. Isolated sporophylls are known as LepidostrobophyllumLepidondendron became almost completely extinct by the end of the Westphalian.
Lepidodendron Hans' (Steur) Paleobotany Page reconstruction showing different organs 
 
 
Lepidodendron
Lepidodendron aculeatum  M. Hieb's Plant Fossils of West Virginia figured upside down
Lepidodendron aculeatum Geol.-Paläontol. Museum, Universität Münster  
Lepidodendron aculeatum  Fossils of Nova Scotia  
Lepidodendron obovatum  Museum of Natural History, Sendai German material  in a Japanese museum !
Lepidodendron obovatum M. Hieb's Plant Fossils of West Virginia  
Lepidodendron worthenii M. Hieb's Plant Fossils of West Virginia  
Lepidodendron Fossils of Nova Scotia  
Lepidodendron Fossils of Nova Scotia  
Lepidodendron Fossils of Nova Scotia foliated branches
Lepidodendron Fossils of Nova Scotia  
Lepidodendron Fossils of Nova Scotia  
Lepidodendron Fossils of Nova Scotia decorticated axis
Lepidodendron Manny's Fossil Gallery  
Lepidodendron M. Hieb's Plant Fossils of West Virginia  
Lepidodendron  M. Hieb's Plant Fossils of West Virginia specimen showing Ulodendron aspect
Lepidodendron
M. Hieb's Plant Fossils of West Virginia specimen showing Ulodendron aspect
Lepidodendron Mazon Creek Exhibit, Illinois State Museum   
Lepidodendron M. Hieb's Plant Fossils of West Virginia branching
Lepidodendron
Kansas Fossils, Geol. Museum, Emporia State Univ.       
Lepidodendron Collection Jens-Wilhelm Janzen  
Lepidodendron and Stigmaria R.A. Spicer, The Open University, Milton Keynes  
Lepidodendron Kathleen Pigg's "Plant Fossils and Evolution"   
Lepidodendron Kathleen Pigg's "Plant Fossils and Evolution"  coal ball: cross section of a stem
Lepidodendron Bot. Soc. America, Online Image Collection coal ball: cross section, small stem
Lepidodendron Bot. Soc. America, Online Image Collection as above, high resolution
Lepidodendron selaginelloides Bot. Soc. America, Online Image Collection coal ball; leaf base with ligule
Lepidodendron Bot. Soc. America, Online Image Collection as above, high resolution
Lepidodendron Bot. Soc. America, Online Image Collection coal ball: cross section
Lepidodendron Bot. Soc. America, Online Image Collection as above, high resolution
Lepidodendron Fossil plants from the Northern Anthracite Coal Field  
Lepidodendron  Virtual Paleobotany Laboratory  
Lepidophyllum (this genus is also known as Cyperites or Lepidophylloides)
Lepidophyllum sp. M. Hieb's Plant Fossils of West Virginia small foliated axes
Lepidophyllum sp. M. Hieb's Plant Fossils of West Virginia  as above, one with cones
Lepidophyllum sp. Mazon Creek Exhibit, Illinois State Museum  
Lepidophylloides  Virtual Paleobotany Laboratory  
Lepidophylloides Virtual Paleobotany Laboratory  
Cyperites bicarinatus Fossil plants from the Northern Anthracite Coal Field  
Lepidostrobus
Lepidostrobus sp. Mazon Creek Exhibit, Illinois State Museum  
Lepidostrobus sp. M. Hieb's Plant Fossils of West Virginia  
Lepidostrobus  Collection Jens-Wilhelm Janzen  
Lepidostrobus Fossil plants from the Northern Anthracite Coal Field  
Lepidostrobus Fossils of Nova Scotia  
Lepidostrobus Fossils of Nova Scotia  
Lepidostrobus Virtual Paleobotany Laboratory coal ball peel showing anatomy 
Lepidostrobus Virtual Paleobotany Laboratory coal ball peel showing anatomy 
Lepidostrobus sp. Paläobotanik Münster anatomically preserved
have a look ! 
Lepidostrobophyllum
Lepidostrobophyllum sp. Mazon Creek Exhibit, Illinois State Museum  
Lepidostrobophyllum sp. M. Hieb's Plant Fossils of West Virginia  
Lepidostrobophyllum lanceolatum Fossils of Nova Scotia  
Lepidostrobophyllum Virtual Paleobotany Laboratory  
Lepidophloios differs from Lepidodendron in having diamond-shaped leaf cushions that wider than high but also spirally arranged. This tree had the same type of rooting and foliage types as Lepidodendron.
Lepidophloios laricinus  Fossils of Nova Scotia  
Lepidophloios laricinus  Fossils of Nova Scotia  
Lepidophloios laricinus  Fossils of Nova Scotia  
Lepidophloios Virtual Paleobotany Laboratory  
Lepidophloios sp. Paläobotanik Münster
 
have a look ! 
Lepidocarpon is a megasporophyll holding a megasporangium with only a single functional megaspore. The megapsporophyll encloses the megasporangium completely thus giving optimal protection. The whole unit (megasporophyll + megasporangium) is shed from the cone. Lepidocarpon thus already pretty much shows a seed-like morphology. 
Lepidocarpon Virtual Paleobotany Laboratory  
 
Sigillaria is another very common and widepread lycopod tree. Leaf cushions are rhomboidal in outline and usually placed in distinct vertical rows; in some species rows are separated by rigdes. Unlike Lepidodendron, Sigillaria did not branch very often, usually one or two times. Rooting systems and leaves are of the same type as in Lepidodendron. The strobili, known as Sigillariostrobus, were borne directly on the main stem. Most Sigillaria species became extinct by the end of the Westphalian but a few forms survived and persisted into the Permian.
Sigillaria  Museum of Natural History, University of Michigan  reconstruction of a tree 
Sigillaria M. Hieb's Plant Fossils of West Virginia reconstruction of a tree
Sigillaria
Sigillaria sp. M. Hieb's Plant Fossils of West Virginia decorticated stem
Sigillaria brardii Fossil plants from the Northern Anthracite Coal Field  
Sigillaria Fossil plants from the Northern Anthracite Coal Field decorticated axis
Sigillaria Collection Jens-Wilhelm Janzen  
Sigillaria Manny's Fossil Gallery  
Sigillaria Virtual Paleobotany Laboratory  
Sigillaria scutellata  Fossils of Nova Scotia  
Sigillaria elegans Fossils of Nova Scotia  
Sigillaria tessalata Fossils of Nova Scotia  
Sigillaria tessalata Fossils of Nova Scotia  
Syringodendron sp. M. Hieb's Plant Fossils of West Virginia decorticated Sigillaria
Sigillariostrobus
Sigillariostrobus sp. M. Hieb's Plant Fossils of West Virginia  
Stigmaria is the rooting system of tree lycopods, Lepidodendron, Lepidophloios and Sigillaria. The woody, a few times bifurcating axes borne hollow tube-like appendages which had the function of roots.  Such rooting systems are called rhizomorphic; Isoetes is one of the very few modern lycopods with a rhizomorphic rooting system. Stigmaria rootlet beds are very common and often occur underneath coal seams. Most famous are in situ preserved forest stands with several stigmarian tree trunks, e.g. the Fossil Grove in Glasgow (Scotland) and Joggings (Nova Scotia).
Stigmaria ficoides M. Hieb's Plant Fossils of West Virginia  
 
 
Stigmaria Manny's Fossil Gallery  
Stigmaria ficoides  Fossils of Nova Scotia  
Stigmaria ficoides  Fossils of Nova Scotia  
Stigmaria ficoides  Fossils of Nova Scotia  
Stigmaria ficoides Fossils of Nova Scotia  
Stigmaria sp Fossils of Nova Scotia  
Stigmaria Bot. Soc. America, Online Image Collection cross section
Stigmaria Bot. Soc. America, Online Image Collection as above, high resolution
Stigmaria Virtual Paleobotany Laboratory  
Stigmaria Virtual Paleobotany Laboratory  
Stigmaria Virtual Paleobotany Laboratory anatomically preserved
Several examples of fossil lycopod forests are known. These forests consist of upright standing tree stumps, i.e. the rooting system and the lower portion of the stem. The Fossil Grove in Glasgow (Scotland) and Joggins (Nova Scotia) are among the most famous. 
The Fossil Grove Hunterian Museum Glasgow  
Joggins    
Chaloneria is was an up to 2 m high unbranched  heterosporous lycopod with axes up to 10 cm in diameter with roots of the Stigmaria-Isoetes type. The microspores are of the Endosporites type, whereas the megaspores are of the Valvisisporites type. This taxon is known from North American coals balls.
Chaloneria Kathleen Pigg's "Plant Fossils and Evolution"  longitudinal section through the base
 
 
Chaloneria Kathleen Pigg's "Plant Fossils and Evolution"  cross section
Chaloneria   Kathleen Pigg's "Plant Fossils and Evolution"  bark and outer stem surface
Chaloneria Kathleen Pigg's "Plant Fossils and Evolution"  phloem
Chaloneria Kathleen Pigg's "Plant Fossils and Evolution"  fertile and vegetative stems
Endosporites Kathleen Pigg's "Plant Fossils and Evolution"  microspores of Chaloneria
Valvisisporites Kathleen Pigg's "Plant Fossils and Evolution"  megaspore of Chaloneria
Chaloneria  Kathleen Pigg's "Plant Fossils and Evolution"  megagametophyte
Chaloneria  Kathleen Pigg's "Plant Fossils and Evolution"  megagametophyte
Chaloneria  Kathleen Pigg's "Plant Fossils and Evolution"  megagametophyte
Chaloneria  Kathleen Pigg's "Plant Fossils and Evolution"  megagametophyte
Lycopodites is a genus for small, herbaceous lycopods
Lycopodites  Kathleen Pigg's "Plant Fossils and Evolution"  
 
 
Lycopod megaspores
Thomasonia Bot. Soc. America, Online Image Collection  
Thomasonia Bot. Soc. America, Online Image Collection as above, high resolution
Minerisporites mirabilis Bot. Soc. America, Online Image Collection  
Minerisporites mirabilis Bot. Soc. America, Online Image Collection as above, high resolution
Molaspora lobata Bot. Soc. America, Online Image Collection  
Molaspora lobata Bot. Soc. America, Online Image Collection as above, high resolution
Megaspore of Lepidodendron Virtual Paleobotany Laboratory  
Some information on modern lycopods
Modern lycopods Univ. California Museum of Paleontology, Berkeley  
 
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Disclaimer

The last check of the list of links was done on 25 October 1999. 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!  
Suggestions for improvement and hints to other internet resources are most welcome

  
© Forschungsstelle für Paläobotanik, Westfälische Wilhelms-Universität Münster 
October 1999