Fossils, the impressions or mineralized remains of ancient organisms, provide the most concrete evidence of birds' evolutionary past. However, the relatively lightweight skeletons of birds are far from ideal material for fossilization.

In 1861, a fossil of Archaeopteryx (Latin for ancient wing), the first known bird, was discovered. Archaeopteryx, which lived 140 million years ago, is significant because it had characteristics of both reptiles and modern-day birds. In addition to feathers, Archaeopteryx had teeth and reptile-like claws on the wings.

Another Jurassic bird species, Confuciusornis, was found in China. Like Archaeopteryx, it was feathered and had large claws on the forelimbs. Both Archaeopteryx and Confuciusornis belong to an archaic bird group that died out at the end of the Cretaceous Period.

Select this text to learn about some of the ancient birds discovered trapped in the Rancho La Brea Tar Pits.