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Temporal range: Carboniferous
|The strobilus (sporangia-bearing part) of Lepidodendron|
They were huge, over 30 metres (100 feet), and the trunks were often over 1 m (3.3 ft) in diameter.
The river plain which was the heart of the wetland stretched across Pangaea 5000 km from eastern Canada to the Ukraine, and was 700 km wide.p6 This would make the Pennsylvanian basin larger than any wetlands on Earth today.
Change of climate
The rainforest system collapsed about halfway through the Pennsylvanian, and was replaced by a cooler, drier climate.
The wetland forests ended when the land level was raised by the pressure of the Gondwana continent against Laurussia, causing the zone of contact to be raised. The end of the Coal Measures marks the end of the Carboniferous period. China was too far away to be affected, and there the wetland forests continued for another 50 million years, into the early Permian.p30
Lepidodendron had tall, thick trunks that rarely branched and were topped with a crown of bifurcating branches bearing clusters of leaves. These leaves were long and narrow, similar to large blades of grass, and were spirally-arranged.
The closely packed diamond-shaped leaf scars left on the trunk and stems as the plant grew provide some of the most interesting and common fossils in Carboniferous shales and accompanying coal deposits. These fossils look much like tire tracks or alligator skin.
The scars, or leaf cushions, were composed of green photosynthetic tissue, evidenced by the cuticle covering and being dotted with stomata, microscopic pores through which carbon dioxide from the air diffuses into plants. Likewise, the trunks of Lepidodendron would have been green, unlike modern trees which have scaly, non-photosynthetic brown or gray bark.
Lepidodendron has been likened to a giant herb. The trunks produced very little, if any, wood. Most structural support came from a thick, bark-like region. This region remained around the trunk as a rigid layer that did not flake off like that of most modern trees. As the tree grew, the leaf cushions expanded to accommodate the increasing width of the trunk.
- Thomas B.A. and Cleal C.J. 1993. The Coal Measure forests. National Museum of Wales.