Definition - What does Pennsylvanian Period mean?
Pennsylvanian Period is a period that began 355 million years ago and lasted for about 64 million years. It was first characterized by the appearance of reptiles and widespread swampy forests. Well developed tree rings, less diverse flora and fauna were also common at the time. Due to the global climatic changes, the Pennsylvanian Period came to an end 289 million years ago.
Petropedia explains Pennsylvanian Period
During the sixth period of Paleozoic era, many minerals like shale, coal, sandstone, and limestone occurred on the surface. The period was subdivided into 4 main stages as per the international time scale. They are Bashkirian, Moscovian, Kasimovian, and Gzhelian. Apart from 700 kinds of cockroaches, one of the greatest revolutionary innovations of the period was the amniote egg that led to the growth of tetrapods. In the upper regions, limestone was the major constituent whereas the lower part was heavily marine. The period proves profitable as the extensive amount of plant material from the forests led to high production of coal.