Evolution of Birds

Most ornithologists believe that birds evolved from dinosaurs. The first known species of bird, the archaeopteryx, lived about 150,000,000 years ago. Although it had feathers and wings, it also had reptilian features, such as teeth, claws on all four limbs, and a long, bony tail. The sinornis was a type of bird that lived shortly after the archaeopteryx; it had a shorter tail and a more efficient type of wing than the archaeopteryx.

Fossil birds of North America were the ichthyornis, which resembled a gull, and the hesperornis, a water-dweller about five feet (1.5 m) long with sharp teeth. By about 75,000,000 years ago, the types of birds we know today had begun to develop.