“UP, UP, AND AWAY”
THE EARLIEST BIRDS
145 million years ago
|Reconstruction of the earliest known bird, Archaeopteryx.
Credit: Illustration by John Sibbick, courtesy of John Sibbick Illustration. This illustration is used with permission. All rights reserved.
Bird-watchers are fascinated by the diversity and beauty of our fine-feathered friends, and humans have envied the freedom and gracefulness of their flight for thousands of years. Birds are a warm-blooded class of vertebrates characterized by feathers, wings, and, for most, the ability to fly. How far back can we trace such creatures in the fossil record? Beginning around 152 to 168 million years ago some smaller reptiles began to develop feathers, probably first to help regulate body temperature and later selected for flight. The earliest known feathers found on reptiles in China may have developed to provide warmth, rather than flight. Birds are believed to have evolved from a form of small, bipedal theropod dinosaur, and birds are considered by most paleontologists to the one group that survived the dinosaur extinction 65 million years ago.
By 145 million years ago fossils of Archaeopteryx, discovered in a limestone quarry in Germany, show adaptations for flying in a crow-sized animal. Adaptations for flying in such fossils include a well-developed sternum or breastbone for the attachment of flying muscles and feathers asymmetric in cross-section characteristic of modern birds of flight. Interestingly, these early birds retained a number of reptilian features such as teeth, claws in its upper limbs (wings), and a long tail.
|This Archaeopteryx lithographica fossil is displayed at the Museum fÜr Naturkunde in Berlin, Germany. Archaeopteryx is the earliest and most primitive bird specimen found so far. It lived in the late Jurassic period, about 150-148 million years ago.
Credit: Photo by H. Raab (User:Vesta)/ Wikipedia.
HOW DO WE KNOW?
Early bird fossils from well-dated deposits sometimes show, in fine detail, the impressions of feathers, showing that some of these reptiles were evolving into birds. In addition to Archaeopteryx, other early birds include the Confuciusornis, Yanornis, Ichthyornis, and Gansus. In addition to evidence of feathers in Archaeopteryx, many of the Chinese theropod fossils show spectacular preservation of feathers, and one was tested and found to contain the characteristic protein found in bird feathers.
WHY SHOULD I CARE?
Birds are an essential part of our environment, being a major factor in pest control of insects. They also play a role in pollinating plants and are very important in dispersing their seeds. Domestic chickens (and their eggs), turkeys, ducks, and geese are an important part of many peoples’ diets as well.
This Nature article describes the new discovery of Aurornis Xui, an even earlier bird ancestor than Archaeopteryx lithographica.
This is a National Geographic article that supports the argument that theropods gave rise to modern birds.
This is a National Geographic article on the earliest known bird embryo, with colorful illustrations based on the fossil embryo found.
This is another National Geographic article that talks about a fossil that links dinosaurs to birds.