File:Aneurophyton fossil land plants (Devonian; Gilboa, southeastern New York State, USA) (15334958580).jpg

Aneurophyton fossil land plants from the Devonian at Gilboa, southeastern New York State, USA. (public display, FMNH P21741, Field Museum of Natural History, Chicago, Illinois, USA)

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.

These are branches from an extinct group of vascular plants, the aneurophytalean progymnosperms. Progymnosperms have characteristics of seed plants (they have lots of gymnosperm-like wood - secondary xylem) and characteristics of ferns (fern-like reproductive structures that produce spores). Aneurophyton is a progymnosperm with non-flattened branches that emerge from the main axis of the plant in a helical or decussate (successive branch pairs are oriented at 90 degree angles from each other) fashion. The photosynthetic structures in Aneurophyton are not true leaves - they are usually referred to as “pre-leaves”. This plant produced spores having one morphology but a range of sizes (70 to 150 μ in the same plant). Aneurophyton has been reported from the Devonian of Europe, Russia, and America.