Lycopod Plant Fossils

{ By the Devonian Period, vascular plants had colonized the land and large, tree-like forms appeared along with smaller plants. A large tree present in the Late Devonian was Archaeopteris. Large logs, representing the trunks of Archaeopteris trees are not uncommon in the Ohio Shale. These dark, coalified logs were originally given the name Callixylon. Remains of other plants, sometimes well preserved, are occasionally found in the Cleveland Member of the Ohio Shale in the Cleveland area. These were plants that grew on the Catskill delta, to the east, in western Pennsylvania, and drifted out into the sea in which the Ohio Shale was deposited.

Remains of lycopods are sometimes found in marine rocks of Mississippian age but they are not common. These remains represent terrestrial vegetation that drifted to sea from the Catskill delta to the east.

In contrast, rocks of Pennsylvanian age are rich in lycopod remains. These trees, which reproduced by means of spores, dominated the coal swamps and were a major contributor to the organic material that eventually would become coal. Many of these trees were large, with heights of nearly 100 feet and trunks of more than three feet in diameter. Lycopods bore leaves near the top of the tree. As fossils, they are most easily identified by diamond-shaped leaf scars that cover the trunk in a spiral fashion. Generally, the fossils are preserved as sandstone or siltstone casts of the trunk. People sometimes mistake these trunks for [[Category:{$topic}]]