Fossil data reveal the origin of feathers

(scienceinfo.net) - How did birds form wings? Fossil data show that the proportion of limbs changed in dinosaur-derived birds.

The bird originated from a small group of theropod dinosaurs and is a carnivorous dinosaur known as maniraptoran dating back about 150 million years ago. Recent findings from around the world show that a lot of maniraptoran is very similar to birds, with feathers, hollow bones, small body size and high metabolic rate.

Professor Hans Larsson of McGill University and a graduate instructor, Alexander Dececchi, have found the answer to the question by examining fossil data, which has really expanded in recent years. From the time of the appearance of the first birds.

In a study published in September in Evolution (Lars), Larsson and Dececchi found that in most of the history of carnivorous dinosaurs, leg length showed a stable proportional relationship to the size. Body size.

Although Tyrannosaurus rex (Tyrannosaurus) is 5000 times heavier than the smallest and hairy theropods in China. The leg rate has changed, however, in the ancient birds, both the forelimbs and the back limbs have experienced an incredible separation from body size. This change may be urgent in allowing the first ancient birds to fly and then explore the sky of the jungle, the authors conclude.

When the forelegs were long, they became long enough to be used as a wing, allowing an evolution of active flying (using the body's energy flight). Once separated with the short contraction of the posterior limbs, this helped the ancient bird fly better and more efficiently. Shorter legs helped in reducing drag during flight - the reason that modern birds bend their legs when they fly - and also to park and move on small branches on trees. The combination of such better wings with thicker legs can help the birds survive during periods of flying reptiles, lizards, and dominate the sky and compete for food.

'The results of our research have shown that birds have undergone a sudden change in their development mechanisms, such as the front limbs and the posterior limb became a problem for length control. Differences, " said Larsson. The changes from the principles of animal limb proportions to changes in body size - another example is the association between long limbs and short arms in children. People - often a sign of a major change in function or behavior. 'This separation may be the basis for the success of the most diverse species of birds and vertebrates on Earth. nowadays".

'The origin of birds and flying using energy is a major evolutionary change in class' , Dececchi said, now a postdoctoral study at the University of South Dakota. 'What we found showed that bird's feet length had to be separated from normal body size before they could spread so successfully. It is possible that this truth is what allows them to become more of a breed of maniraptoran and lead them to expand the range of shapes and sizes of limbs that we see in today's birds. "

'This study, along with our previous studies, that the ancestors of birds did not stand up, to clarify the premise of bird ecology,' Dr Dececchi said. 'Knowing the origin of birds, and the way they are present today, is a key issue to understand how the modern world changes to look like today.'

The study was financially supported by many scientific research agencies of the Canadian government.