"We know that dinosaurs developed "hands" with digits one, two and three -- which are the same as the thumb, index and middle fingers of humans -- because digits four and five remain as tiny bumps or vestiges on early dinosaur skeletons," Feduccia said. "Apparently dinosaurs developed a very specialized, almost unique "hand" for grasping and raking.
"Our studies of bird embryos, however, show that only digits two, three and four develop, and this creates a new problem," he said. "How do you derive a bird "hand," for example, with digits two, three and four from a dinosaur hand that has only digits one, two and three" The answer is that you can't."
Additionaly reserchers point to some other differences:
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.
"We know that dinosaurs developed "hands" with digits one, two and three -- which are the same as the thumb, index and middle fingers of humans -- because digits four and five remain as tiny bumps or vestiges on early dinosaur skeletons," Feduccia said. "Apparently dinosaurs developed a very specialized, almost unique "hand" for grasping and raking.
They explain dinosaur/bird similarities by proposing that dinsaurs and birds shared a common ancestor and both were adapting to upright posture.
If other researchers confirm the results this could be big.
