Ornithurae
Ornithurae is a clade of birds that lived from the Cretaceous period to the present day. This group is characterized by a number of skeletal features, most notably the fusion of the last caudal vertebrae into a pygostyle, which supports the tail feathers. Unlike earlier bird groups such as Enantiornithes, Ornithurae birds possessed a fused sternum with a keel for the attachment of flight muscles. They also had a fully ossified, fused tarsometatarsus and tibiotarsus, contributing to their increased agility and stability in flight.
The fossil record shows that Ornithurae emerged during the Early Cretaceous, with early representatives like *Confuciusornis*