Wednesday, 25 January 2012

New Research Suggests That Archaeopteryx Could Indeed Fly

The holotype fossil of Archaeopteryx lithographica,
 discovered at the Solnhofen limestone quarry in Bavaria,
 Germany in 1861
150 years ago, a mysterious fossil was excavated at a limestone quarry at Solnhofen in Bavaria. It was purchased a few years later by Sir Richard Owen, curator and founder of the Natural History Museum, London. The fossil was of course Archaeopteryx, the strange intermediate form between dinosaurs and birds. Its relationships with other animals has long been in dispute, changing between theropods and avians. The most recent conclusion is that it is the first bird, rather than feathered reptile.

One thing that has always been a mystery is whether the creature could fly. Now a team of scientists, led by Ryan Carney from Brown University, believe that they have found the first concrete evidence which suggests that Archaeopteryx was capable of powered flight.

When comparing the structure of flightless birds to those which can fly, an obvious difference presents itself. Flightless birds do not have very rigid feathers. Instead their feathers are soft and downy. Winged birds on the other hand have strong feathers which can support their body weight in the air without bending or splitting. It is impossible to tell from looking at a bird fossil with the naked eye whether the feathers were rigid of downy. Yet the researchers employed a novel technique to distinguish between the two.

Melanosomes are small structures within cells which contain pigments. These pigments determine the colour of the tissue. A study, conducted around six months ago by Yale graduate student Jacob Vinther, found a way to study melanosomes within fossils, allowing an accurate colour picture of an organism to be built up.

Melanosomes are different across tissue groups: ones found in downy feathers are different to those in flight feathers. By studying the wing impressions on Archaeopteryx, the team found that the raven-sized bird had black feathers and rigid wings which would have enabled it to fly. Its ancestral feathered dinosaurs probably had downy feathers as they had no need to fly. Therefore the feather difference between Archaeopteryx and its ancestors suggests that it had evolved powered flight.

'We can't say it's proof that Archaeopteryx was a flier. But what we can say is that in modern bird feathers, these melanosomes provide additional strength and resistance to abrasion from flight, which is why wing feathers and their tips are the most likely areas to be pigmented' Carney said.' With Archaeopteryx, as with birds today, the melanosomes we found would have provided similar structural advantages, regardless of whether the pigmentation initially evolved for another purpose.'