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Which fossils provide evidence that birds descended from dinosaurs?
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Bird
A brightly colored zebra finch (Taeniopygia guttata) perched on a branch.
Extensive fossil evidence confirms that birds evolved from a lineage of small theropod dinosaurs. This evolutionary link is supported by numerous remarkably preserved fossils, particularly those discovered in the Liaoning province of China, which display filamentous, featherlike structures.123
Key fossils providing this evidence include:
- Archaeopteryx: Long considered the oldest known bird, this genus shares many anatomical features with coelurosaurs, including teeth, a long tail, and a wishbone. It is now often classified as a feathered dinosaur.45
- Sinosauropteryx: A dinosaur fossil covered in a thick "pelage" of dark, hair-like filaments, providing early evidence of non-avian dinosaurs with integumentary structures similar to feathers.12
- Xiaotingia zhengi: A birdlike fossil that, alongside Archaeopteryx, helps demonstrate the close evolutionary relationship between birds and theropods.42
- Caudipteryx and Protarchaeopteryx: These fossils possess true feathers, indicating that feathers evolved in dinosaurs for purposes such as insulation or display long before the advent of flight.2
These findings demonstrate that many characteristics once thought unique to birds—such as feathers, hollow bones, and specific wrist structures—were already present in their non-avian dinosaur ancestors.432