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March 29, 2006

Evolution: Dinosaur to Bird theory

Summary:
Demise of the "Birds are Dinosaurs" Theory

Two startling studies, relying on completely different methods, published just three weeks apart, have dealt a "one-two punch to the dinosaurs origins of birds hypothesis" according to paleontologist James Farlow of Indiana University-Purdue University at Fort Wayne. The first study examined the origins of the three bones of the fingers/wings and feet of the theropod dinosaurs and modern birds. The results clearly indicated that the hands of the theropod dinosaurs are derived from digits I, II, and III, whereas the wings of birds, although they look alike in terms of structure, are derived from digits II, III, and IV. The second study looked at the lungs of the theropod dinosaurs (from fossil evidence) and compared them to the lungs of modern reptiles and birds. The results indicated that the theropod dinosaurs likely possessed a diaphragm and bellows-like septate lungs (similar to modern reptiles), which are not found in modern birds. In addition, the theropod dinosaurs lacked the proper pelvic structure to assist breathing by means of tail movements. Such structures are incapable of supporting warm-blooded respiration and the aerobic requirements of flight.

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