Geology of Ohio terrestrial environment since the Permian. For instance, the main subdivisions of the Pennsylvanian: the Pottsville Group, Alleghany Group, Conemaugh Group and Monongahela Group, along with the Early Permian Dunkard Group, are each more terrestrial than the last. The region was situated inland, experiencing terrestrial erosion as the Proto-North American continent of Laurasia collided with Gondwana to form the supercontinent Pangaea. Rocks from the end of Paleozoic are best exposed in road cuts along I-77, between Canton and Marietta, I-77 from Cambridge to Bridgeport and cliffs on the Ohio River north of Marietta to East Liverpool. For 245 million years, spanning
Gondwana and barren landscape. West Gondwana drifted north during the Devonian which brought Gondwana and Laurasia close together. Global cooling contributed to the Late Devonian extinction (19% of marine families and 50% of genera went extinct) and glaciation occurred in South America. Before Pangaea had formed terrestrial plants, such as pteridophytes, began to diversify rapidly resulting in the colonisation of Gondwana. The Baragwanathia Flora, found only in the Yea Beds of Victoria, Australia, occurs in two strata separated by or 30 Ma; the upper assemblage is more diverse and includes Baragwanathia, the first primitive herbaceous lycopod to evolve from the zosterophylls.