Archaeopteryx is the earliest recognized bird that appears in the fossil record. It lived about 150 million years ago. Archaeopteryx possesses both reptilian and birdlike features, providing compelling evidence that birds originally evolved from dinosaurs. It had a head, teeth and claws like a reptile, but a larger brain, feathers and an opposable big toe like birds. Only eight specimens are known, with the first specimen discovered in 1861, two years after Charles Darwin published his Origin of Species. The discovery provided additional evidence that all life forms on Earth ultimately share a common lineage.
Archaeopteryx lived at the same time as a number of feathered dinosaurs, but it was the first to seriously depart from the dinosaur line in terms of anatomy. It is still not agreed upon whether or not Archaeopteryx had the ability to fly, but it almost certainly did glide. Its brain size is sufficient to support the coordination of flight, but its lack of a strong breastbone throws doubt on the hypothesis. Most likely, Archaeopteryx had the ability to run and glide, allowing it to escape from predators more rapidly, and progressively longer gliding eventually evolved into full-fledged flight. Archaeopteryx had no bill, only a mouth covered with sharp teeth. In contrast, no modern bird possesses teeth.
Archaeopteryx was originally discovered under limestone in Germany, and the Berlin museum possesses the best known specimen to this day. The first specimen was merely a feather, discovered in 1861, but full specimens were discovered about every 20 years after that. The first full specimen, known as the "Berlin specimen," was discovered in Germany in 1876.
Archaeopteryx has separated vertebrate, rather than birds which always have fused vertebrate. Archaeopteryx has slender, regular ribs, rather than ribs which articulate outwards at the sternum, as in modern birds. Not all the metacarpals are fused together, as in most birds. Archaeopteryx is fascinating to paleontologists because of the extreme transitional nature of the species.