The oldest known syrinx (vocal organ) of a bird has been found, preserved in three dimensions in a 66-million-year-old specimen from Antarctica, according to new research led by a University of Texas at Austin paleontologist.
In a Nothofagus forest on the shoreline of Vega Island, Antarctica, a mid-sized raptor dinosaur is shown using close-mouth vocal behavior and Vegavis iaai is flying overhead. Image credit: Nicole Fuller / Sayo Art / University of Texas at Austin.
This discovery and the apparent absence of syrinx in non-avian dinosaur fossils of the same age indicate that the organ may have originated late in the evolution of birds and that other dinosaurs may not have been able to make noises similar to the bird calls we hear today.
“This finding helps explain why no such organ has been preserved in a non-avian dinosaur or crocodile relative,” said lead author Dr. Julia Clarke, from the Jackson School of Geosciences at the University of Texas at Austin.
“This is another important step to figuring out what dinosaurs sounded like as well as giving us insight into the evolution of birds.”
The fossilized syrinx was found in a specimen of Vegavis iaai, an extinct species of bird that lived between 68 and 66 million years ago.
It was unearthed more than two decades ago on Vega Island, Antarctica. However, it wasn’t until 2013 that Dr. Clarke noticed that the fossil included a syrinx.
The asymmetrical shape of the syrinx indicates that Vegavis iaai could have made honking noises via two sound sources in the right and left parts of the organ.
Dr. Clarke and co-authors also scanned syrinxes of other birds to compare with the Vegavis syrinx. This included 12 syrinxes from living birds and the next oldest fossilized syrinx, which had not yet been studied.
“Here, we begin to outline how fossilizable characteristics of the syrinx may inform us about sound features, but we need a lot more data on living birds,” said co-author Dr. Franz Goller, from the University of Utah.
“Remarkably, prior to this work, there is almost no discussion of these important questions.”
“The evolution of vocal behavior can give insights into other anatomical features, such as the appearance of bigger brains,” Dr. Clarke added.
This study follows research that Dr. Clarke and her colleagues published earlier this year that found some dinosaurs would likely have made closed-mouth vocalizations akin to ostrich booms that don’t require a syrinx.
“Together, the two studies have major implications for dinosaur sound-making throughout time,” Dr. Clarke said.
“The origin of birds is about so much more than the evolution of flight and feathers,” she added.
The discovery is reported Oct. 12 in the online edition of the journal Nature.
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Julia A. Clarke et al. Fossil evidence of the avian vocal organ from the Mesozoic. Nature, published online October 12, 2016; doi: 10.1038/nature19852
