How Walking Dinosaurs Evolved into Flying Birds: They Shrank

It turns out that the dinosaurs that survived were the ones that shrank. Scientists have taken a closer look at the dinosaur family tree and have found how massive, meat-eating, ground-dwelling dinosaurs evolved into agile flying birds.

A branch of dinosaurs, called the theropods, gave rise to modern birds. This group of dinosaurs was the only one that kept getting smaller over time. In addition, they evolved new adaptations such as feathers, wishbones, and wings about four times faster than other dinosaurs.

In order to learn more about the evolution of dinosaurs, the researchers examined over 1,500 anatomical traits of dinosaurs in order to reconstruct their family tree. Then, they used mathematical modelling in order to trace evolving adaptations and changing body size over time and across dinosaur branches.

"Birds evolved through a unique phase of sustained miniaturization in dinosaurs," said Michael Lee, the lead author of the new study, in a news release. "Being smaller and lighter in the land of giants, with rapidly evolving anatomical adaptations, provided these bird ancestors with new ecological opportunities, such as the ability to climb trees, glide and fly. Ultimately, this evolutionary flexibility helped birds survive the deadly meteorite impact which killed off all their dinosaurian cousins."

In fact, the researchers found that the branch of dinosaurs that eventually evolved into birds was more evolutionary innovative than other dinosaur lineages.

"Birds out-shrank and out-evolved their dinosaurian ancestors, surviving where their larger, less evolvable relatives could not," said Lee.

The findings reveal a bit more about how dinosaurs evolved. This, in turn, can tell researchers a bit more about modern birds and how they came to be.

The findings are published in the journal Science.