The Karoo is a semidesert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its extent is also not precisely defined. The Karoo is partly defined by its topography, geology and climate, and above all, its low rainfall, arid air, cloudless skies, and extremes of heat and cold. The Karoo is also known for its exposure of the fossiliferous rocks of the Karoo Supergroup, which records in detail ecological change in the region when it formed part of southern Pangaea from the Middle Permian to the Early Jurassic, around 270 to 200 million years ago.