In the early Cretaceous, a superb range of coelurosaurian fossils (including avians) are known from the Yixian Formation in Liaoning. All known theropod dinosaurs from the Yixian Formation are coelurosaurs. Many of the coelurosaurian lineages survived to the end of the Cretaceous period (about 66 Ma) and fossils of some lineages, such as the Tyrannosauroidea, are best known from the late Cretaceous. A majority of coelurosaur groups became extinct in the Cretaceous–Paleogene extinction event, including the Tyrannosauroidea, Ornithomimosauria, Oviraptorosauria, Deinonychosauria, Enantiornithes, and Hesperornithes. Only the Neornithes, otherwise known as modern birds, survived, and continued to diversify after the extinction of the other dinosaurs into the numerous forms found today.