Mammals evolved from a reptilian ancestor group include Dimetrodon that gave rise to the Therapsids. This transition is a major event in evolution of life begun approximately 250 million years. The most prominent feature of Dimetrodon is the large neural spine sail on its back formed by elongated spines extending from the vertebrae similar to crested chameleon. The fossils of these early mammals have played a central role in understanding both mammalian evolution and the theory of plate tectonics which explains how animals have made it from South Africa to Antarctica without a land connection between the
