Third, he said, if one views a chicken skeleton and a dinosaur skeleton through binoculars they appear similar, but close and detailed examination reveals many differences. Theropod dinosaurs, for example, had curved, serrated teeth, but the earliest birds had straight, unserrated peg-like teeth. All dinosaurs had a major joint in the lower jaw that early birds did not. Birds have a reversed rear toe that opposes the front three toes and allows birds to perch. Dinosaurs had no reversed toe.
Birds grow a girdle of bone in their chests quite different from dinosaur chests.
The new work involved microscopic examination of early limb development in ostriches, chickens, cormorants, alligators and turtles and comparison of chick fore- and hindlimbs. The answer is that you can't. Findings from the examination of alligator and turtle embryos were consistent with those of birds, the biologist added. Far more likely is that birds and dinosaurs had a much older common ancestor, he said. Many superficial similarities between birds and dinosaurs arose because both groups developed body designs for walking upright on two hind legs and began to resemble each other over millions of years.