Tree-perching birds
The debate as to whether Archaeopteryx could or could not fly still continues. It has been argued that Archaeopteryx was too heavy and that its muscles were to light to power it, and that they used their feathers for gliding or cooling themselves. Some researchers have argued that Archaeopteryx had the muscles of a cold-bloodedreptile. These are twice as powerful per unit weight as those of warm-blooded animals, and may have allowed Archaeopteryx to fly short distances which makes more ecological sense than a warm-blooded Archaeopteryx possessing wings and feathers but not the ability to fly.
Now with the discovery of a fossil bird in northeastern China which has provided the first evidence that fairly modern tree-perching birds had evolved by 135 million years ago, only 15 million years after Archaeopteryx.
Now with the discovery of a fossil bird in northeastern China which has provided the first evidence that fairly modern tree-perching birds had evolved by 135 million years ago, only 15 million years after Archaeopteryx.
This sparrow-sized bird, which is as yet unnamed, has an opposable first digit and slender claws on its legs. This would have allowed it to firmly grasp a tree banch and to "perch" (the flat forward pointing claws of Archaeopteryx mark it as a ground-dwelling animal). This small bird had a well developed keel on its sternum which was the anchor site for strong flight muscles and also possessed a pygostyle (fused cluster of tail vertebrae to which long tail feathers are attached). This gave the bird a centre of gravity in the centre of the wings, whereas the long-feathered tail of Archaeopteryx puts the centre gravity well back of the wing and just above its feet which is a better position for an animal that runs. This Chinesebird did, however, retain some primitive traits. These include small remnants of claws and fingers, stomach ribs and the bird may have had teeth. All of these are present in Archaeopteryx and carnivorousdinosaurs but not in modern birds. This Chinesefossil does present problems such as how an animal like Archaeopteryx could have evolved into this bird like animal within 10 - 15 million years?
