06.21.00--The most common lycopod fossil is probably the Lepidodendron. The rounded, diamond-shaped structures arranged in rows (in the photograph to the left) are leaf cushions and scars. Lepidodendron bore its leaves directly on the trunk in spiral rows. The roots, leaves, and cones of this tree are also known as independent fossils, and each structure has a different name. The roots are called Stigmaria; the leaves are called Lepidophyllum; and the cones are called Lepidostrobus.

Lycophytes, or lycopods include the most primitive trees. They were dominant in the coal swamps of the Mississippian and Pennsylvanian Periods of the Devonian Age. Much of the coal mined in North America today comes from the leaves, trunks, and stems of these plants, some of which grew to heights of more than 100 feet. There are only three genera of living lycopods. They are called club mosses and are very small.