Ferns were well represented in the Late Paleozoic coal swamps. They reproduce by means of spores found under the leaves. Ferns ranged from small, shrubby forms similar to those we see today, to tree-ferns, such as the Permian Pecopteris, the most common fossil tree fern.

Pteridospermates are a group of extinct seed ferns, which were not really ferns but primitive gymnosperms. Although their foliage resembled that of modern ferns, they reproduced by means of seeds instead of spores.

The seed ferns underwent increased diversity during the Carboniferous. The isolated leaf fossils are difficult to distinguish between ferns and seed ferns. Often seed ferns had the leaf fossil known as Neuropteris associated with the seeds.