Hypothetical former supercontinent in the Southern Hemisphere, which included modern North America, Europe, and Asia (except peninsular India). The concept that the continents were at one time joined was first set forth in detail by Alfred Wegener in 1912. He envisioned a single great landmass, Pangea, which supposedly began to separate early in the Jurassic Period (approximately 200 million to 146 million years ago). Subsequent research distinguished between a northern landmass, Laurasia, and Gondwana. Laurasia is thought to have fragmented into the present continents largely during the end of the Cretaceous Period and the beginning of the Paleogene Period. See alsocontinental drift.