While it's clear simply from looking at the skulls of dinosaurs and modern birds that the two creatures are vastly different dinosaurs have distinctively long snouts and mouths bristling with teeth, while birds have proportionally larger eyes and brains it was the realization that skulls of modern birds and juvenile dinosaurs show a surprising degree of similarity that sparked the study.
"No one had told the big story of the evolution of the bird head before," Bhullar said. "There had been a number of smaller studies that focused on particular points of the anatomy, but no one had looked at the entire picture. What's interesting is that when you do that, you see the origins of the features that make the bird head special lie deep in the history of the evolution of Archosaurs, a group of animals that were the dominant, meat-eating animals for millions of years."
To tackle the problem, the researchers turned to an unusual methodology. Using CT scanners, they scanned dozens of skulls, ranging from modern birds to theropods the dinosaurs most closely related to birds to early dinosaur species. By marking various "landmarks" such as the orbits, cranial cavity and other bones in the skull on each scan, researchers were able to track how the skull changed shape over millions of years.
"We examined skulls from the entire lineage that gave rise to modern birds," Abzhanov said. "We looked back approximately 250 million years, to the Archosaurs, the group which gave rise to crocodiles and alligators as well as modern birds. Our goal was to look at these skulls to see how they changed, and try to understand what actually happened during the evolution of the bird skull."
What Abzhanov and colleagues found was surprising
|Contact: Peter Reuell|