Pennsylvanian
From EvoWiki
The Pennsylvanian was the first sub-period of the Carboniferous period lasting from roughly 325 to 299 million years ago. The Pennsylvanian saw the evolution of the first undisputed reptile Hylonomus around 314 million years ago. The Pennsylvanian witnessed the high point of primitive stem tetrapod evolution and primitive synapsids made their appearance during the Pennsylvanian and early synapsids and reptiles eventually replaced the stem tetrapods as the most successful group of tetrapods during the Paleozoic at the end of the Pennsylvanian sub-period. Also the Pennsylvanian sub-period saw the appearance of the order of large dragonfly like insects known as the Protodonata which included the species Meganeura monyi which had a wingspan up to a meter wide. On the land, swamps and forests continued to expand throughout the equator and the tropics and hosted a variety of flora, such as tree ferns which grew to 15 meters (or 49.2125 feet) in height and primitive conifer-like plants which often grew as tall as 40 meters (or 131.233 feet). The Paleozoic supercontinent Pangaea first formed in the late Pennsylvanian as a result of a collision between the supercontinents Gondwana and Laurasia. The majority of coal used by humans comes from coal deposits dating back to the Pennsylvanian that were the remains of rotting vegetation which existed in the forests of the Pennsylvanian sub-period.
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