In Paleontology, however, these wing digits have been considered as digits 1, 2 and 3 based on phylogenetic assessment of the fossil lineage suggesting that birds have evolved from theropod ancestors that had lost the fourth and fifth digits. Critics of this theory have suggested that birds have evolved from some other ancestors that had lost the first and fifth digits. Studies of developing limbs of chicken, including a polydactylous variety and mouse have confirmed that the wing digits are actually 1, 2 and 3 and support the hypothesis of theropod descent of birds. (Vargas; Fallon, 87)

Conclusion:

The origin of birds from dinosaurs is a fascinating study. The discovery of the first fossil protobird, the Archaeopteryx started most of the studies on the dinosaurian origins of birds. Most paleontologists now agree that birds have descended from a particular line of dinosaurs, the theropods, more specifically the coelurosaurs who had...
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