Archaeopteryx is the earliest known bird. When it was first discovered in Germany in 1861, it was hailed as the missing link between birds and dinosaurs and proof for the theory of evolution. This crow-sized animal lived about 150 million years ago and had feathers identical to that of modern flying birds. But Archaeopteryx also had sharp teeth, a long bony tail and clawed fingers. Recent studies reveal that it also had long feathers on its back and legs; this suggests that the first birds were four-winged gliders that coasted between treetops like flying squirrels.