Avialae

Avialae is a term for birds and their immediate extinct ancestors. It is a clade of dinosaurs containing their only living representatives (birds) and whatever coelurosaurs are regarded as their ancestors. There are two ways it can be defined:

Avialae
Scientific classification
Kingdom:	Animalia
Superorder:	Dinosauria
Order:	Saurischia
(unranked):	Paraves

Definition by physical characters

Avialae is defined as a clade based on physical characteristics. Jacques Gauthier named Avialae in 1986 as all dinosaurs that possessed feathered wings used in flapping flight, and the birds that descended from them.^[1][2]

Branch-based definition

Several other authors use a similar, but branch-based, definition: all theropods closer to birds than to Deinonychus.^[3][4]

References

1. Gauthier, J. 1986. Saurischian monophyly and the origin of birds. In: K. Padian ed. The origin of birds and the evolution of flight. San Francisco: California, Acad.Sci. pp.1–55. (Mem.Calif.Acad.Sci.8.)
2. Gauthier J. and de Queiroz K. 2001. Feathered dinosaurs, flying dinosaurs, crown dinosaurs, and the name Aves. 7-41 in New perspectives on the origin and early evolution of birds: proceedings of the International Symposium in Honor of John H. Ostrom (J.A. Gauthier and L.F. Gall eds) Peabody Museum of Natural History, Yale University, New Haven, Connecticut.
3. Weishampel, David B.; Dodson, Peter; Osmólska, Halszka (eds) 2004. The Dinosauria. 2nd ed, University of California Press.
4. Senter P. 2007. A new look at the phylogeny of Coelurosauria (Dinosauria: Theropoda). Journal of Systematic Palaeontology, (doi:10.1017/S1477201907002143).