The true fern "Pecopteris" also grew in West Virginia during the Pennsylvanian. Fossil ferns include "Pecopteris" and the tree ferns "Megaphyton" and "Caulopteris". As of 1997, there have been 250-300 species assigned to "Pecopteris". Most "Pecopteris" leaves and fronds are associated with the marattialean tree fern "Psaronius". Pecopteris is a very common form genus of leaves. "Pecopteris" is derived from the Greek "pekin", (to comb), and "pteris", (a fern).