Fossilised feathers from a four-winged dinosaur that lived 160 million years ago have shed fresh light on the evolution of flight.
Roughly the size of a pheasant, Anchiornis roamed China 10 million years before Archaeopteryx – the first recognised bird.
Chemical analysis found its preserved feathers had the same proteins found in birds today.
Although they were not suitable for powerful flight, their molecular composition may signify an intermediate stage in the evolution of bird feathers.
The flight feathers of modern birds are mainly composed of a protein called beta-keratin (β-keratin) which gives them special bio-mechanical properties such as flexibility, elasticity and strength to meet the needs of flight.
Anchiornis’ feathers were predominated by thicker alpha-keratin proteins (α-keratins) rather than thinner β-keratins.
Co-author Professor Mary Schweitzer, a biological scientist at North Carolina State University, said: ‘Modern bird feathers are composed primarily of beta-keratin (β-keratin) – a protein also found in skin, claws and beaks of reptiles and birds.
‘Feathers differ from these other β-keratin containing tissues because the feather protein is modified in a way that makes them more flexible.
‘At some point during the evolution of feathers, one of the β-keratin genes underwent a deletion event – making the resultant protein slightly smaller.
‘This deletion changed the biophysics of the feather to something more flexible – a requirement for flight.
‘If we can pinpoint when, and in what organisms, that deletion event occurred, we will have a better grasp on when flight evolved during the transition from dinosaurs to birds.’