Unlike humans, birds don’t have voice boxes or vocal cords. The organ that allows them to produce songs and sounds is called a syrinx. There’s a big gap in what scientists know about the origins of this organ, because while birds are closely related to dinosaurs, syrinx fossils are fairly rare. Now, scientists have discovered the oldest fossil evidence of the syrinx in Antarctica, and it dates back between 66 and 68 million years, according to a recent study in the journal Nature [PDF].

The preserved syrinx was found in the partial skeleton of a bird from the Late Cretaceous period on Vega Island, located just off the Antarctic Peninsula. It belonged to Vegavis iaai, an extinct bird related (but likely not ancestral) to modern ducks and geese. The fossil was discovered way back in 1992, according to The New York Times, but the lead author of the present study, paleontology Julia Clarke, only thought to examine its vocal structures and look for the syrinx in 2013. 

J. Clarke/UT Austin

 
As you can see in the image above, the syrinx is located deep within birds’ chests, branching into both the right and left lungs. Clarke and her team used CT tomography scans to compare the fossilized syrinx to those of 12 other modern birds and the next-oldest fossil syrinx ever discovered in an attempt to reconstruct the evolution of the organ.

The researchers hypothesize that few other fossilized syrinx examples have been found because it’s a relatively newer feature in bird evolution, and is much younger than some of birds’ other respiratory developments or the ability to fly, which came about during the dinosaur age. Non-avian dinosaurs probably didn’t have these vocal organs, this study suggests, although the evidence isn’t entirely conclusive.

It’s hard to imagine what the dinosaur world sounded like, but this suggests that while avian dinosaurs might have honked in a similar way to geese, using a syrinx, non-avian dinosaurs didn’t make those noises. Clarke’s research has previously pointed to dinosaurs making cooing or bellowing sounds similar to crocodiles. Either way, they probably weren’t roaring.