Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from earlier continental units approximately 335 million years ago, fully assembled about 270 million years ago, and it began to break apart about 175 million years ago. In contrast to the present Earth and its distribution of continental mass, much of Pangea was in the southern hemisphere and surrounded by a super ocean, Panthalassa. Pangea was the most recent supercontinent to have existed and the first to be reconstructed by geologists.