Birds developed the unique vocal organ that enables them to sing more than 66 million years ago when dinosaurs walked the Earth, a new fossil discovery has shown.
But the earliest syrinx, an arrangement of vibrating cartilage rings at the base of the windpipe, was still a long way from producing the lilting notes of a song thrush or blackbird.
Scientists believe the extinct duck and goose relative that possessed the organ was only capable of making honking noises.
The bird, Vegavis iaai, lived during the Cretaceous era. Although its fossil bones were unearthed from Vega Island in Antarctica in 1992, it was not until three years ago that experts spotted the syrinx.
All birds living today are descended from a particular family of dinosaurs that developed feathers and the ability to fly.
The new discovery suggests the syrinx is another hallmark of birds that was absent from non-avian dinosaurs.
Dr Julia Clarke, from the University of Texas at Austin, US, who led a study of the fossil syrinx published in the journal Nature, said: "This finding helps explain why no such organ has been preserved in a non-bird dinosaur or crocodile relative.
"This is another important step to figuring out what dinosaurs sounded like as well as giving us insight into the evolution of birds."
Unlike the human voice box, or larynx, the syrinx does not employ vocal cords but instead consists of stiff, cartilage rings that vibrate to produce sound.
Cartilage does not mineralise as well as bone, making it rare in the fossil record.
So far the Vegavis syrinx remains the only one known to scientists from the age of the dinosaurs.
The researchers are now comparing the organ with its equivalent in living birds in search of clues about how the earliest birds may have sounded.
"The origin of birds is about so much more than the evolution of flight and feathers," Dr Clarke said.
She led a previous study reported earlier this year showing that some dinosaurs would probably have made closed-mouth noises similar to ostrich "booms", that do not require a syrinx.