Therapsida
Therapsida, is a clade of the class Synapsida, traditionally referred to as order. Terapsids are the ancestors of mammals. The terapsids emerged in the Permian period, at the end of the Paleozoic era, being descendants of the pelicans. From the mid-Permian, they became the dominant group of animals on Earth, with several suborders and families occupying many ecological niches. Many species disappeared in the event of mass extinction occurring at the end of the Permian period, but the surviving species were able to adapt and reached the Triassic period, already in the Mesozoic era, once again reaching great diversity. However, at the end of the Triassic, there was another major extinction and the terapsids virtually disappeared and were replaced as the dominant group by the emerging dinosaurs. A few species lasted until the end of the Cretaceous, when at last they disappeared.