The story of birds and their evolution is rather sketchy. Bird skeletons made of slender and hollow bones do not fossilise well. However, we do have some idea how they originated. During excavations at the German limestone quarries where so many reptiles have been found, a puzzling discovery was made. This quarry dates from the Jurassic Period, some 150 million years ago, when the Age of Reptiles was at its height. On a piece of stone the workmen found the imprint of a feather. Was this from a bird, and what was it doing among all these reptiles? The idea that it came from a bird was confirmed shortly afterwards when a finely preserved skeleton turned up, on which the feathers of the wings and tail were clearly marked. This is the earliest known feathered creature, called Archaeopteryx (the 'ancient wing') of which three specimens have been found.
This rook-sized creature turned out to be a kind of reptile covered in feathers. It had teeth, a long tail and claws on its wings. In fact, the actual skeleton was very much like that of a lizard. Modern birds have no teeth or claws on their wings, and a short tail. Rarely do we find such precious fossils which form a link between two different groups of animals.
By the Cretaceous Period, a number of true birds had evolved, the ancestors of our modern birds. They were mostly water birds. From these we can recognise a large diving bird, called Hesperornis. It had no wings and was shaped like a large grebe. Another, called Ichthyornis, could fly, and resembled a tern.
