Birds are sometimes referred to as glorified reptiles, and even though modern birds are structurally very different from reptiles.Some show minor evidence of their ancestry, like scales on their feet, or claw on their toes. However, flying reptiles disappeared more than 70 million years ago, but birds have obviously managed to survive. You remember that biological success of any group of organism is measured by the number of species and individuals in the group. There are distributions through all around the world and of course their ability to adapt to all kinds of environmental conditions. On the basis of these criteria, birds are considered as one of most successful vertebrate in modern times. Their success means they were probably not only better adapted than reptiles for flying, but also for life on land and water. But when did glorification begin? And how fast did the changes occur? It was seen logical to assume that at some time millions of years ago transitional stages between reptiles and birds existed. And in fact, one of the most important clues came with the discovery of the fossils called archaeopteryx which literally means ancient bird.The archaeopteryx dates back 150 million years to the Jurassic period. Fortunately, the fossils are not only included the skeleton, but also impression of the feathers of the wings and double rare tails feathers. If it were not for these feathers, scientists would have classified it as the reptile because it have many characteristics more like a lizard than a bird. Archaeopteryx is not, however, considered as the ancestor of modern birds. But it probably was deprived from ancestral form that also gave rise to modern birds.Up until the mid-1980s,archaeopteryx was considered the most ancient of all birds. Then in 1986, a fossil was discovered called protoavis that show a mixture of dinosaur and bird-like characteristics. But it lived 225 million years ago, about 75 million years before archaeopteryx. So clearly the final work is not yet in on the origin of birds.