to think, to think ....

Birds (Aves) are a class of warm-blooded vertebrates, characterized by the presence of feathers, toothless beak, laying of eggs, high metabolic rate, four-part heart and a solid light skeleton with frequent bone fusion. They are a surviving, specialized group of theropod dinosaurs (maniraptors) that were the only ones to survive extinction at the end of the Cretaceous 66 million years ago.