A team of scientists led by Julia Clarke of the University of Texas reconstructed the so-called voice box of a 68-year-old bird fossil that lived in Antarctica at the time of the dinosaurs. Their findings suggest that the extinct creature may have produced honk-like or quack-like sounds like modern ducks. This study, published in the journal Nature, provides interesting information about the evolution of birdsong.
Scientifically known as Vegavis iaai, the bird belongs to the group of swans, ducks, and geese. The small and sleek creature was discovered on Vega Island in the Arctic Peninsula over twenty years ago.
The study lead author said this is the first time researchers pay close attention to the origin of birdsong. In contrast, the evolution of the wing in birds has been widely studied and discussed.
For this particular study, the research team reconstructed the evolution of the oldest-known fossil of a syrinx, the small bony organ responsible for the sound production in birds as it sits near the heart. The syrinx is composed of soft tissues and rings of thick cartilage.
They achieved this by scanning the fossil specimen with micro-CT, which is an X-ray scanning technique not much different from the one used in hospital CT scans. The scientists then made a 3D representation of the voicebox and compared it with younger fossils and a dozen living birds by using a different type of imaging that allowed them to look closer at soft tissues.
Prof. Clarke said this complicated but exciting process allowed the team to conclude that the oldest fossil was capable of honks and whistles, as reported by the BBC. The study was only possible because the specimen had been perfectly prepared for most of the rock around the syrinx had been removed, which allowed Clarke to identify the voicebox while she and her colleagues were analyzing the remains in high resolution.
The syrinx’s soft tissue is generally cleared away from fossils. In this case, the rock matrix had not been removed from the spot where the organ was supposed to be. It would have been lost otherwise. Plus, Clarke had already started a project to study vocalization in avian dinosaurs, which helped her clearly detect there was a syrinx on this ancient fossil.
The team of scientists estimated that the fascinating organ appeared late in birds’ evolution, which implicates that the origin of flight arose well before the animals’ ability to sing. Clarke believes the syrinx came sometime during the Cretaceous period, about 145.5 million years ago.
Non-bird dinosaurs may have never developed a voicebox
When thinking about the sound landscape at the time of the dinosaurs, Prof. Clarke’s team deduced earlier this year that some non-bird dinosaurs might have produced a booming, deep noise. She told BBC News that larger animals most likely would have produced lower frequency sounds overall.
The study authors searched for previous research on non-avian dinosaurs and didn’t find evidence of syrinx-like structures. They now know that the only creatures capable of developing this particular organ were would-be birds.
However, Clarke said the scientists were eager to find out how earlier this structure appeared for the first time. She pointed out that researchers used to believe that feathers were unique to creatures capable of flying, but then found that many non-flying dinosaurs also developed this feature.
The researchers are eager to answer more questions about the origins of birdsong
The study lead author also suspects that flying may have resulted in a variety of different sounds depending on the voicebox’s shape.
“We think it evolved after some of the respiratory innovations linked to the evolution of flight, sometime after that but before that bird ancestor,” Clarke said, according to The Washington Post. “But we can’t be sure yet. What would be ideal is more data.”
Further research is also needed to have a more accurate understanding of the frequency range or the variety of sounds birds produce. Clarke noted that the research team needs to construct models and get more information from today’s birds to fully understand the range of sounds the syrinx can produce.
Prof. Patrick O’Connor of Ohio University said the diversification of birds might have been a result of the syrinx origin.
“Their amazing diversity may in part be related to the evolution of the syrinx and any areas of the brain related to sound production and reception in the context of social interactions more generally,” he explained.