Panthalassa

Panthalassa, also known as the Panthalassic Ocean or Panthalassan Ocean (from Greek πᾶν "all" and θάλασσα "sea"),[1] was the superocean that surrounded the supercontinent Pangaea. During the Paleozoic–Mesozoic transition  c. 250  Ma  it occupied almost 70% of Earth's surface. Its ocean floor has completely disappeared because of the continuous subduction along the continental margins on its circumference.[2] Panthalassa is also referred to as the Paleo-Pacific ("old Pacific") or Proto-Pacific because the Pacific Ocean developed from its centre in the Mesozoic to the present.