Archaeopteryx

Archaeopteryx, small, feathered dinosaur that is known from fossils found in rock that was deposited during the late Jurassic Period, about 150 million years ago. Its name is derived from the Greek words arkhaios, “ancient,” and pteryx, “wing.” Scientists have found several fossil specimens of the archaeopteryx in limestone sediments that were deposited in shallow lagoons in what is now southern Germany. The beautifully preserved fossils indicate that the archaeopteryx had characteristics that were less specialized for flight than those of some birdlike dinosaurs that lived later in the age of dinosaurs. The archaeopteryx’s bones were more solid than those of modern birds, which have hollow, light bones to facilitate flight. The archaeopteryx lacked other traits of modern birds, such as strong wings, a compact body, and well-formed neck and tail supports. However, its wing feathers were fully streamlined for flight. Despite the archaeopteryx’s birdlike characteristics, its body more closely resembled those of small meat-eating dinosaurs than it did those of more birdlike dinosaurs.

The archaeopteryx was about as large as a crow but lacked a beak and had a more slender chest area than do modern birds. It had claws on its wingtips, and its tail feathers were supported by a long bony tail rather than by long quills, as in modern birds. It did not hop but could run well, using its tail for balancing and turning. Its brain was smaller than those of most modern birds, and the animal probably did not sing but may have squawked. Its plumage color is unknown. Comparisons of growth rings in the fossils of primitive birds with those of the archaeopteryx suggest that the archaeopteryx had a smaller frame and matured at a slower rate. Thus, the growth ring comparisons suggest that the archaeopteryx had a lower metabolic rate than did birds and other birdlike reptiles of the dinosaur era. The comparisons also suggest that the archaeopteryx had a slower growth rate and metabolic rate than those of modern birds. Nevertheless, it was probably capable of powerful bursts of flight and gliding. Unlike modern migrating birds, it could not fly long distances. This characteristic suggests that it remained in relatively warm, temperate climates. This fact also implies that the archaeopteryx was probably cold-blooded like other reptiles, unlike modern birds, which are warm-blooded and thus have a relatively constant body temperature that enables them to live in a wide variety of environments.

Analysis of its jaws and teeth suggest that the archaeopteryx fed on insects rather than seeds. It hunted during the day, using its large eyes to navigate, find prey, and avoid predators. It found shelter in trees. Fossils indicate that insects were abundant and diverse in its habitat and that lizards and small meat-eating dinosaurs shared the archaeopteryx’s environment of forests and thick underbrush. In a world without birds, the archaeopteryx must have been a highly successful animal.

Most dinosaurs lacked the feathers and particular skeletal specializations for flight possessed by most modern birds. While the terms “dinosaur” and “bird” are not interchangeable, the animals do share some similar traits. For example, in the 1990s scientists discovered fossils of downy feathers associated with the skeletons of two kinds of small, flightless dinosaurs, Protarchaeopteryx and Caudipteryx, in northeastern China. Caudipteryx appears to resemble other small, nesting dinosaurs whose remains have been found in Mongolia. In addition to feathers, these dinosaurs also possessed a primitive birdlike furcula, or “wishbone,” as well as long arms with birdlike wrists. Many skeletons of true birds have been found in the same rock layers, which were deposited in ancient lakes early in the Cretaceous Period, about 135 million years ago. These fossils indicate that feathered, flightless dinosaurs and true birds not only shared the same habitats but were also related to one another. When their common feathered ancestors are found, probably in lake deposits of the middle Jurassic, the ancestors may well resemble a large, flightless archaeopteryx. The archaeopteryx is thus identified by many paleontologists as the so-called missing link between early reptiles and modern birds and is therefore one of the most instructive guides in the study of evolution.