Perhaps you ask, "Why feathers?" The evidence for feathers comes from discoveries in the late 1990's of incredibly well preserved feathered dinosaurs including raptor-type dinosaurs found in Laioning Province in northeastern China. Further clues indicating dinosaur feathers are found by comparing a tail structure called a pygostyle that is found in both modern birds and bird-like dinosaurs such as oviraptorids. The individual tail vertebrae found in early birds such as Archaeopteryx were later fused into a pygostyle, a bone to which cartilage and tail feathers attach.

 

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Courtesy of StoneCompany.com

Feathered dinosaur from Laioning. Shows 5 individual tail vertebra present in ancient birds that later fused into a pygostyle.

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Courtesy of StoneCompany.com

Closeup of the "Eichstatt" Archaeopteryx specimen showing tail vertebra.

New evidence for dinosaur feathers continues to be brought to light to help solve the mystery. The unveiling of the new feathered dinosaur from China at the AMNH on April 26, 2001 is the most convincing evidence yet. Many different theories about the presence or absence of feathers are still argued though the evidence for feathers grows stronger with each new discovery. Some scientists believe that young dinosaurs may have had downy feathers for warmth rather than for flight.

Dinosaur detectives continue to study other clues that may link dinosaurs and birds. Maniraptoran theropod dinosaurs (raptor-type dinosaurs including oviraptorids) had a furcula and fused clavicles. Both are used in modern birds for large flight muscles. The semilunate carpal (wrist bone) was present in bird-like dinosaurs as well as in birds. It is an extra bone in the wrist that allows a rotating movement for flapping the wing in flight. The science of dinosaur eggs and embryos is still young. Much is yet to be discovered by future generations of earth science enthusiasts.