The Pennsylvanian might make up a hefty chunk of one of Earth’s most important periods, the Carboniferous ... ranging from insects, to arachnids like spiders and scorpions, to reptiles ...

This time period took place 359 to 299 million years ago. 3 min read The Carboniferous period, part of the late Paleozoic era, takes its name from large underground coal deposits that date to it.