Season 253 - Day 6 of 14

This theoretical supercontinent, whose name derives from Ancient Greek meaning "all the earth," existed during the late Paleozoic and early Mesozoic eras before beginning to break apart roughly 200 million years ago.
Which massive contiguous landmass, first hypothesized by meteorologist Alfred Wegener in 1912 as the foundation for his theory of continental drift, was surrounded by a single global ocean known as Panthalassa?