Vocal organ of a prehistoric bird, illustration. The inset shows the vocal organ, or syrinx, that was found in a fossilised Vegavis iaai bird in Antarctica. It consists of stiff cartilage rings that support soft tissues that vibrate to produce complex sounds. V. iaai lived around 66 million years ago during the Late Cretaceous. Birds evolved from dinosaurs, however, no such vocal organ has been found in dinosaurs that were living at the same time and so it can be concluded that the organ evolved after birds separated from dinosaurs. Without such a vocal organ it is highly unlikely that dinosaurs would have been able to make the same complex vocalisations as birds.