A comprehensive review of feathered dinosaurs has drawn the conclusion that theropods developed the potential for flight three times before early birds came into the picture. Published in the journal Current Biology, the project took several years to finish. The findings rewrite the accepted version of the evolutionary tree.
Now, researchers will work towards configuring a truer representation of how this mode of travel emerged among dinosaurs as well as birds.
Such is the groundbreaking nature of the study that researchers from five different countries were involved.
The study was led by Professors Michael Pittman and Rui Pei at Hong Kong University who oversaw the research.
Together, they examined fossils, looking for species whose anatomy might meet the threshold considered vital for flight.
Potential entries included theropods with smaller bodies, accelerated evolutionary rates, early feathers with complex coloration, flapping-based movement, and avian-like sleeping positions.
With the information gathered, the researchers were then able to develop a new evolutionary tree that focused on the emergence of physical features that had the potential for powered flight.
Many avialan relatives were found to come within touching distance yet only on three occasions did species cross the threshold.
This was once in birds and twice in dromaeosaurids: a family of feathered theropod dinosaurs.
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Controversially, however, the tree indicates that anchiornithine theropods were in fact the earliest birds.
McGill University Professor Hans Larsson, who was a member of the international team of researchers, noted the significance of the research.
She said: “This was a fun collaboration over several years.
“For the first time, we have a well resolved evolutionary tree of these small, feathered dinosaurs to ask questions about how birds originated.
“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.
“This goes against the simple, linear stepping forward through evolution model of bird origins and instead presents one where 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.”