</jcapU/Q:> <P>Why do scientists think birds descended from dinosaurs?</p> <p><P>A: The "overwhelming majority" of specialists in ancient life think birds descended from dinosaurs, says Richard Slaughter, director of the UW-Madison Geology Museum. "When you look at the skeletons of birds and dinosaurs, they share a large number of characteristics that you don't see in any other group."</p> <p>One example is the wishbone, which runs across the breast in birds. "Birds have it, and you can also find it in some meat-eating dinosaurs, including Tyrannosaurus rex, but no other animals have it," Slaughter says. "This is one reason we think birds descended from meat-eating dinosaurs."</p> <p>Estimates of the number of skeletal characteristics shared by birds and dinosaurs, but found nowhere else, reach up to 120, Slaughter says.</p> <p>In recent years, scientists have unearthed more information about the oldest known bird, called Archaeopteryx, which had well-developed feathers and lived in the late Jurassic period, about 150 million years ago. "A number of discoveries have really tightened the association between birds and dinosaurs," Slaughter says.</p> <p>With some of the new specimens, "It is getting difficult to distinguish what is an early bird and what is a dinosaur. People often ask, 'Where are these transitional forms?,' but there have been so many transitional forms coming out of China that it's almost hard to put a boundary that says, 'these are birds, these are dinosaurs.' "</p> <p></jend> - Produced in cooperation with University Communications

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