BIO220H1 Lecture Notes - Lecture 24: Thoracic Vertebrae, Carpal Bones, Thoracic Cavity
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Birds therefore sacrificed weight so that they could have the ability to resist twists and fractures. Weight reduction in birds were necessary, one of the ways was the evolution of really large eyes. Many birds have very reduces pre-maxilla and maxillas. If jaws were just like this, these birds would be quite fragile. Birds furthermore have no teeth and urinary bladder, all of this urine gets stored in the urinary bladder. Water is unbelievably heavy, so when birds produced urine they produce uric acid. The transition from the reptilian shape to the generalized bird shapes. First is the modification of wings, the first observable thing is that the humerus is shorter and wider than the radius and ulna, which is likewise elongated. Their carpals are quite fixed, the rest of the arm are fused with the bird"s hands. The carpus and meta carpus -> fuse into carpometacarpus.
