A NEW family tree shows every bird living today is a cousin of the king of the dinosaurs, Tyrannosaurus Rex, the most fearsome predator that ever walked the earth.
But researchers say there is “no single missing link” when the prehistoric creatures transformed into modern birds.
Evidence shows meat-eating dinosaurs that walked upright slowly acquired bird-like features over tens of millions of years.
Analysis of fossil remains suggests there followed an evolutionary explosion that spawned the thousands of avian species on the planet today.
The findings suggest avian evolution took off once basic traits such as feathers, wings and wishbones had been assembled.
“There was no moment in time when a dinosaur became a bird, and there is no single missing link between them,” said Dr Steve Brusatte, from the University of Edinburgh’s School of GeoSciences, who led the research.
“What we think of as the classic bird skeleton was pieced together gradually over tens of millions of years.
“Once it came together fully, it unlocked great evolutionary potential that allowed birds to evolve at a supercharged rate.”
The scientists analysed the anatomical make-up of more than 850 body features in 150 extinct species and combined the findings with statistical techniques to build up the most detailed avian family tree to date.
The results confirmed the emergence of birds 150 million years ago was a gradual process, with some dinosaurs becoming more bird-like over time.
Tyrannosaurus rex was a theropod, a large family of dinosaurs that stood on two legs and included the largest land-dwelling carnivores that have ever lived. All birds are descended from theropods.
The findings support a theory first proposed in the 1940s that suggested the emergence of new body shapes in groups of species could trigger an evolutionary surge.
Co-author Dr Graeme Lloyd, from Oxford University, said: “Our study adds to a growing number of works that approach this problem from different angles, but all seem to confirm that the origin of birds was a truly special event in earth history.
“It is particularly cool that it is evidence from the fossil record that shows how an oddball offshoot of the dinosaurs paved the way for the spectacular variety of bird species we see today.”
The latest findings come just days after palaeontologists in the United States revealed they had found a new species of duck-billed dinosaur that roamed the earth around 75 million years ago.
The giant swamp-dweller has been named Rhinorex Condrupus, meaning King Nose, on account of its most distinguishing feature.
Weighing in at a massive 8,500lb and measuring about 30ft long, the beast had one of the biggest body-to-nose ratios of any dinosaur yet discovered.
The fossil was first uncovered in the 1990s in Utah’s Nelsen rock formation but had until recently been lying in storage.
It was only after painstakingly reconstructing the skull that Terry Gates, from North Carolina State University, and Rodney Sheetz, from Brigham Young University, realised it was a new species.