A new family tree of meat-eating dinosaurs showed how these ancient creatures paved the way for modern-day birds.
The findings show bird-like features such as "feathers, wings and wishbones" slowly developed in dinosaurs tens of millions of years ago, Swarthmore College reported.
The findings also suggest once a functioning bird body shape was developed there was an "evolutionary explosion" that rapidly led to the thousands of avian species that fly the skies today.
The researchers looked at the anatomical makeup of more than 850 features in 150 extinct species and performed a statistical analysis to create an extremely detailed family tree. The analysis suggested the emergence of birds 150 million years ago was a gradual process in which dinosaurs slowly became more bird-like.
"The evolution of birds from their dinosaur ancestors was a landmark in the history of life. This process was so gradual that if you traveled back in time to the Jurassic, you'd find that the earliest birds looked indistinguishable from many other dinosaurs," said Swarthmore College Associate Professor of Statistics Steve C. Wang.
Wang invented the groundbreaking technique that revealed how dinosaurs slowly evolved into birds before the "explosion" of development. The new findings support a controversial theory from the 1940s that suggested the emergence of new body types could lead to this kind of rapid development. If this is true, there is a much larger gray area in the distinction between dinosaurs and birds.
"There was no moment in time when a dinosaur became a bird, and there is no single missing link between them, " said Steve Brusatte of the University of Edinburgh's School of GeoSciences, who led the study. "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 super-charged rate."
The study results were published in a recent edition of the journal Current Biology.
