Douglas Harper's Etymology Dictionary
Wikipedia
Panthalassa ( Greek πᾶν "all" and θάλασσα "ocean"), also known as the Panthalassic Ocean, was the vast global ancestral Pacific 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 developed from it in the Mesozoic to the present.
In the map shown here, the Earth's equator was a line that roughly crossed the spot where Spain, Casablanca ( Morocco) and Boston ( U.S.) met. South of that line, the land mass is referred to as Gondwana. North of the line, it is referred to as Laurasia.
In the map, the Panthalassa Ocean is depicted as an empty ocean. Plate tectonic studies have argued that during the Paleozoic and Mesozoic small fragments, or terranes (currently preserved at the North American and Asian margins), were drifting across the ocean plate until they accreted at the surrounding continental margins.
Usage examples of "panthalassa".
Now the Earth was composed of only two units: a single enormous continent, called Pangaea, that stretched virtually from pole to pole with Africa at its center, and a single ocean, called Panthalassa, that covered the rest of the globe.
Pangaea teemed and Panthalassa was even more diverse, supporting an amazing array of fish, shellfish, corals, and marine reptiles.