Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
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The Pennsylvanian
Pennsylvanian Animal Life
Plant Life and the Coal Forests
Pennsylvanian Climate and Tectonics
Annularia stellata, an extinct tree-like horsetail
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Carboniferous Tree Fern
Fossil spider
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Pennsylvanian 322–299 mya
Defining Characteristics:
  • • “Coal Age,” very well known for plant fossils that make up the world’s major coal seams
  • • Map of the Pennsylvanian World
Secondary Characteristics:
  • • “Age of Amphibians,” including the ancestors of modern terrestrial vertebrates
  • • diversification of terrestrial and aquatic insects.
  • • evolution of amniotic egg in reptiles

The Pennsylvanian Subsystem was named for Pennsylvania, home of some of North America’s richest coal seams. The name was coined in 1891 by Henry S. Williams for the Upper Carboniferous rock layers of North America. Like Mississippian, the term Pennsylvanian was used more commonly by American geologists because the coal-rich Upper Carboniferous was more easily distinguished from the limestone-rich Lower Carboniferous in North America than in Europe. The International Commission on Stratigraphy has now formalized the division of the Carboniferous into two Subsystems, the Mississippian and Pennsylvanian, replacing the terms Lower Carboniferous and Upper Carboniferous.

During the Pennsylvanian, most continents were connected in one landmass and the world was in the throes of an ice age. Nonetheless, tropical plant growth was very lush. Huge, dense forests of ferns, tree ferns, club mosses, horsetails, and seed-bearers (newly evolved in the Late Devonian Period) occupied many terrestrial niches. Lowland swamps accumulated the dead leaves, trunks, and branches of countless generations of vegetation. Repeated for tens of millions of years, this process laid down peat that would later become some of the major coal seams of the world.

Abundant creatures inhabited the swamps, forests, and surrounding areas. Foremost among these organisms were an ecologically diverse array of hexapods, especially winged insects. These animals served as the main terrestrial herbivores of the time, a niche not yet filled by vertebrates (vertebrate herbivory would evolve later, in the Permian). By late in the Pennsylvanian, virtually all major types of plants and their tissues were consumed by hexapod herbivores and detritivores. Early tetrapods were also diverse. Carnivory and insectivory were the main vertebrate feeding habits in the Pennsylvanian, although some vertebrates, including amphibians as well as early amniote reptiles, may have eaten large fleshy seeds.


Overview | Pennsylvanian Animal Life | Plant Life and the Coal Forests
Pennsylvanian Climate and Tectonics

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