October 21, 2016:

by Sarah Knapton

Dinosaurs were incapable of making the twittering bird-like noises which they are associated with in films like Jurassic Park, scientists have concluded.

Palaeontologists have found the oldest example of a voice-box, dating from the Mesozoic period, around 66 million years ago.

It belonged to an ancient bird from the period, which evolved from earlier dinosaurs.

But crucially, scientists at the University of Texas, discovered that it could not have sung or twittered like birds.

Instead, it could only make honking noises, suggesting the dinosaurs which preceded must also have been confined to a low parp - if they even had a syrinx at all.

Non-avian dinosaurs fossils from the same period do not have syrinx so it is possible that the organ may have originated late in the evolution of birds, meaning dinosaurs may not have been able to make any bird sounds.

In the Jurassic Park series of films the dinosaurs are often heard making trilling, clicking and tweeting noises like birds. But the new study suggests that they are more likely to have sounded like crocodiles.

"This finding helps explain why no such organ has been preserved in a nonbird dinosaur or crocodile relative," said Dr Julia Clarke, a paleontologist at The University of Texas at Austin Jackson School of Geosciences who discovered the fossil syrinx and led the analysis.

"This is another important step to figuring out what dinosaurs sounded like as well as giving us insight into the evolution of birds."

Birds are direct descendants of dinosaurs and are considered living dinosaurs by scientists.

The syrinx is made of stiff, cartilage rings that support soft tissues that vibrate to produce the complex songs and calls of modern birds.

Cartilage does not fossilize as well as hard tissues such as bone. But the high mineral content in the syrinx's rings sometimes allows for fossilization.

The syrinx was found in a fossil of Vegavis iaai, a bird that lived during the Cretaceous. It was discovered on Antarctica's Vega Island in 1992 by a team from the Argentine Antarctic Institute.

However, it wasn't until 2013 that Dr Clarke noticed that the Vegavis fossil included a syrinx. During the past two years, the team searched the dinosaur fossil record for other examples of a syrinx, but so far has found none.

The asymmetrical shape of the syrinx indicates that the extinct species could have made honking noises via two sound sources in the right and left parts of the organ.

This study follows research that Clarke and other collaborators published in July 2016 that found some dinosaurs would likely have made closed-mouth vocalizations akin to ostrich booms that don't require a syrinx.

In addition, the evolution of vocal behaviour can give insights into other anatomical features, Clarke said, such as the appearance of bigger brains.

"The origin of birds is about so much more than the evolution of flight and feathers," Clarke said.

The research was published in the journal Nature.