The term Pennsylvanian was first used by H.S.Williams in 1819 and refers to state Pennsylvania, which the rocks of this period were well exposed and contain abundant coal.
The land flourished with luxuriant plant growth. In addition to horse tails, scouring rushes, club mosses, the woody plants appeared and attained the height of over 100 ft. The most common trees were scale trees. The insect life was most abundant. Dragonflies, Cockroaches etc. attained maximum size. A Dragon fly with a wing span of 20 inches has been unearthed from Belgium.
Amphibians expanded and became more abundant. Labyrinthodonts having somewhat lizard like appearance came into existence. The first reptiles, called stem reptiles, also appeared in Pennsylvanian period. Seymouria from Texas is considered to be the amphibian ancestor to reptiles.