Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Pennsylvanian
Contents
Overview
Pennsylvanian Animal Life
Plant Life and the Coal Forests
Pennsylvanian Climate and Tectonics
Evidence
Annularia stellata, an extinct tree-like horsetail
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sample
Carboniferous Tree Fern
Fossil spider
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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Pennsylvanian Animal Life
The terrestrial animal radiations that had started in the Mississippian continued into the Pennsylvanian. The great coal forests housed enormous insects such as dragonflies (Meganeura) with up to 70-centimeter wingspans, paleodictyopterans with 55-centimeter wingspans, and a variety of large protorthopterans and cockroaches. Other giant terrestrial arthropods included large spider-like animals and a two-meter-long relative of millipedes called Arthropleura. Some of the giant arthropods were early terrestrial herbivores, such as paleodictyopterans with mouthparts adapted for piercing and sucking the juices out of plants, and protorthopterans with chewing mouthparts. These herbivorous insects became food for predaceous arthropods like the dragonflies and scorpions, as well as for early tetrapods. These tetrapods were carnivores (sometimes cannibals) as well as insectivores, but none had yet mastered herbivory. Early amphibians included reptile-like anthracosaurs, snake-like aïstopods, and eel-like semiaquatic forms.

Although amniotes may have evolved as early as the Mississippian, the oldest definitively known amniote fossil is from the Middle Pennsylvanian of Joggins, Nova Scotia. These early "reptilian" skeletal fossils belong to genera such as Hylonomus and Palaeothyris. During the Pennsylvanian, primitive amniotes were able to diversify as they occupied many terrestrial niches and acquired new ecological roles. These primitive amniotes quickly diverged into synapsids (later to include mammals) and diapsids (which would include dinosaurs, crocodilians, birds, lizards, and snakes). These two groups represent nearly all amniotes on Earth today. In addition, more primitive forms called parareptiles appeared as well.


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



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