Dinosaurs were the dominant life form on earth for 170 million years, finally going extinct at the end of the cretaceous period, 65 million years ago, when a huge comet crashed into the Gulf of Mexico. Birds of prey are descended from theropods, a type of dinosaur that walked on its hind legs, while their smaller forelimbs were used, like arms and hands, for reaching and grabbing.
Theropods are usually represented by T-Rex, Allosaurus and Velociraptor, though most theropods were no larger than dogs. During this long period, the earth underwent climate change, just as it does today, and fossilized remains indicate that feathers began to develop about 150 million years ago, and those theropods which developed them survived to breed in cooler temperatures, while those lacking them perished. » Continue Reading.