Some dinosaurs were flying before there were birds, new research suggests
Biologists now have a better idea of the origin of birds and the evolution of flight, two iconic events in the history of life on earth, thanks to work by a group of international scientists including a McGill professor.
In updating the evolutionary tree, the team’s findings show some dinosaurs could fly before they evolved into birds, and many others were experimenting with powered flight.
It also shows behaviour, movements and even anatomies that were traditionally associated with birds were first acquired by non-avian dinosaurs before the origin of birds and modern powered flapping flight.
The updated tree shows powered flight may have evolved in feathered dinosaurs and early birds at least three different times.
The study involved researchers from five countries, and was led by two professors at Hong Kong University, Michael Pittman and Rui Pei. Their findings were published in the scientific journal Current Biology.
"Our revised evolutionary tree supports the traditional relationship of dromaeosaurid (raptors)and troodontid theropods as the closest relatives of birds," said Pei.
Professor Hans Larsson from McGill University in Montreal took part in the study.
“This was a fun collaboration over several years,” said Larsson. “For the first time, we have a well resolved evolutionary tree of these small, feathered dinosaurs to ask questions about how birds originated.”
The team studied fossils and existing evolutionary trees, and estimated how many species may have developed powered flight. The team also used its new and improved evolutionary tree to reconstruct how bird-like theropods would have had the potential for powered flight, referencing the way birds fly today.
“We were able to map biomechanical limits to all these species and propose a picture of experimentation within a spectrum of near-flight to fully-flighted capabilities in these wonderful little carnivores,” said Larsson. “This goes against the simple, linear stepping forward through evolution model of bird origins and instead presents one were an explosive radiation of feathered dinosaurs were experimenting with many kinds of wing-assisted locomotion. I think this is the most realistic view of bird origins to date.”
The improved tree supports the theory that the closest relatives to birds were dromaeosaurids (raptors) and another group of dinosaurs known as the troodontids. It also confirms that anchiornithines were the earliest form of birds.
"The capability for gliding flight in some dromaeosaurids is well established so us finding at least two origins of powered flight potential among dromaeosaurids is really exciting,” said Pittman.