Gondwana was a supercontinent comprising the landmasses of Africa, South America, Australia, and Antarctica, as well as Madagascar and India. It formed when the dynamic forces of plate tectonics split the larger supercontinent of Pangaea in two about 150 million years ago, and it lasted until about 100 million years ago, when it fractured into the individual continents of the Southern Hemisphere.
Recent research shows that Gondwana was home to an almost entirely different set of dinosaurs that evolved in their own unique ways, largely isolated from the dinosaurs we’re more familiar with in the Northern Hemisphere. Thirty years ago, many of these species—including Giganotosaurus, Spinosaurus, and Argentinosaurus—were unknown to science.
Source: Ultimate Dinosaurs: Giants from Gondwana by David C. Evans and Matthew J. Vavrek