Panthalassa (Greek, meaning 'all sea'), also known as the Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea, during the Late Paleozoic and the early Mesozoic eras. It included the Pacific Ocean to the west and north and the Tethys Ocean to the southeast. It became the Pacific Ocean, following the closing of the Tethys basin and the breakup of Pangaea, which created the Atlantic, Arctic, and Indian Ocean basins. The Panthalassic is often called the Paleo-Pacific ("old Pacific") because the Pacific Ocean evolved from it.
In the map on the right, the Earth's equator was a line that roughly crossed the spot where Spain, Morocco (Casablanca), and Boston met. South of that line, the land mass was called Gondwana. North of the line, it was named Laurasia.