Pecopteris fossil ferns on gray, Pennsylvanian-aged mudshale. (10.6 cm across)

Plants are multicellular, photosynthetic eucaryotes. The oldest known land plant body fossils are Silurian in age. Fossil root traces of land plants are known back in the Ordovician. The Devonian was the key time interval during which land plants flourished and Earth experienced its first “greening” of the land. The earliest land plants were small and simple and probably remained close to bodies of water. By the Late Devonian, land plants had evolved large, tree-sized bodies and the first-ever forests appeared.

In the plant fossil record, most leaf fossils are preserved by carbonization, which refers to flattened, dark-colored, carbon-rich films.