Order CETARTIODACTYLA is a large group made up of two very different former orders, the artiodactyls (former order Artiodactyla) and the cetaceans (former order Cetacea). Taxonomists grouped them together after discovering that cetaceans evolved from within the artiodactyls, making the artiodactyls paraphyletic. In this collection, the Cetartiodactyla are divided into these former orders as informal subgroups.