A perfectly preserved fossil of a feathered creature that lived 150 million years ago has provided further evidence to show that modern birds are living dinosaurs.
The fossil is a complete skeleton of an Archaeopteryx and shows it had features common to birds and a group of meat-eating dinosaurs called therapods.
Scientists said the feet of the fossilised Archaeopteryx were anatomically almost identical to those of therapod dinosaurs, which pointed to a common ancestry for both groups. Archaeopteryx had many bird-like features such as feathered wings and a wishbone but it also had distinctly reptilian traits including jaws with teeth, a bony tail and claws on its fingers.
Several fossils excavated in China have shown some dinosaurs also grew feathered wings, which led scientists to suggest that perhaps birds are a living group of specialised meat-eating dinosaurs.
The latest work on Archaeopteryx, the first specimen of which was discovered just two years after Charles Darwin's Origin of the Species was published in 1859, lends further support to the dinosaur origin of birds. Gerald Mayr of the Forschungsinstitut Senckenberg in Frankfurt, Germany and his colleagues describe details of their investigation into the 10th and best-preserved specimen of Archaeopteryx in the journal Science.
The foot is better preserved than any previous Archaeopteryx specimen. It shows a hyperextendible second toe, rather like the killer claw of Velociraptor, the vicious therapod dinosaur depicted in the film Jurassic Park. "These observations provide further evidence for the theropod ancestry of birds," the scientists say. The hyperextendible second toe blurs the distinction between this ancient bird and the therapod dinosaurs, which brings both closer together as a single group, they say.
The therapod dinosaurs ate meat and hunted on two legs, using the claws on their forelimbs to grasp and manipulate their prey.
One theory is that some therapods grew feathers for insulation but these were useful for escaping from larger predators because flapping feathered forelimbs helped the animals to run and jump. This behaviour eventually resulted in gliding and powered flight.
The fossil described by Dr Mayr and his colleagues grew to the size of a magpie and probably lived most of its life on the ground rather than in trees. They say Archaeopteryx had dinosaur-like feet not designed for perching like those of modern birds, with forward and backward-pointing toes. The new fossil, found in the limestone deposits of Bavaria where other specimens have been excavated, also had a head similar to that of a theropod dinosaur with toothed jaws.
Archaeopteryx, which means "ancient wing", was not capable of flying like modern birds and probably flew no more than a few feet at a time.
The Natural History Museum in London owns the first Archaeopteryx specimen to have been discovered, which it bought for £750 in 1862 along with other specimens in a private collection. Now, it is probably the most expensive fossil the museum possesses.
Twenty years ago, some scientists claimed the fossil was a fraud made by sticking feathers into cement around a fossil reptile. But museum scientists soon proved the fossil genuine.