Which dinosaur group gave rise to birds?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Illustration showing various dinosaur species drawn to scale and grouped by geologic era: Late Cretaceous, Early Cretaceous, Jurassic, and Triassic. Dinosaurs range from large species like Brachiosaurus and Tyrannosaurus to smaller ones like Velociraptor and Compsognathus, with a human silhouette included for size comparison. Measurement bars at the bottom indicate 1 meter and 3 feet for scale reference. — dinosaur A selection of dinosaurs grouped by the geologic interval in which they lived.

Modern birds evolved from a lineage of small theropod dinosaurs. Within the theropod group, birds are classified as maniraptorans, a clade that also includes dromaeosaurs and troodontids.123

Scientific consensus, supported by extensive fossil evidence and the analysis of shared anatomical features, confirms that birds are living dinosaurs. These shared characteristics include a similar pelvis structure, long arms and hands, and a unique wrist joint that allows for the side-to-side motion essential for flight. Furthermore, the discovery of numerous theropod fossils with featherlike structures—such as Sinosauropteryx and Caudipteryx—demonstrates that feathers evolved in dinosaurs long before the emergence of flight, likely serving functions such as insulation, display, or camouflage.142