produce an extensive root system, so had a profound impact on soil chemistry. And once these ecosystem changes happened, they were changed for all time. It was a one-time thing." Looking roughly like a top-heavy Christmas tree, Archaeopteris may have played a part in the transformation of Earth's climate during the Devonian before becoming extinct within a short period of time at the beginning of the Carboniferous period. See also Calamites Glossopteris Lyginopteris References External links History of Paleozoic Forests: the Early Forests and the Progymnosperms Consequences of Rapid Expansion of Late Devonian Forests, by Stephen E. Scheckler Walker, Cyril and David Ward. Fossils. Smithsonian Handbooks. Dorling Kindersley, Inc. New York, NY (2002). Mayr, Helmut. A Guide to Fossils. Princeton University Press, Princeton, NJ (1992). Introduction to the Progymnosperms Davis, Paul and Kenrick, Paul; Fossil Plants. Smithsonian Books (in association with the Natural History Museum of London), Washington, D.C. (2004). Late Devonian plants Carboniferous plants Late Devonian first appearances Mississippian genus extinctions Fossil taxa described in 1871 Paleozoic life of Alberta Paleozoic life of Nunavut Paleozoic life of Quebec Prehistoric plant genera