Conceptual illustration of what a Middle Devonian Eifelian Cladoxylopsid and Lycopsid forest may have looked like from fossil forests discovered in Gilboa, Xinhang and Lindlar. Middle Devonian Pseudosporochnales, Cladoxylopsida, Calamophyton and Lycopsid are among the earliest tree-sized plants in the fossil record. Cladoxylopsids are a group of plants known only as fossils that are thought to be ancestors of ferns and horsetails. Lycopsids are related to several extinct groups, including Cooksonia.