The oldest fossilized remains of a syrinx, a bird’s equivalent of a voice box, are described in a study published online in Nature this week. The remains of the extinct bird specimen (Vegavis iaai), which lived about 66-68 million years ago, were found on Antarctica - confirming that the syrinx had evolved at the time of the dinosaurs.
Apart from a few isolated fossils known to be from much younger rocks, the fossil record of the syrinx has been blank up to now.
Julia Clarke and colleagues describe a new syrinx fossil from a partial Vegavis skeleton found on Vega Island on the Antarctic Peninsula. They examine the three dimensional structure of the syrinx using X-ray computed tomography and compare it to data from younger fossils and twelve living birds to reconstruct the evolution of this complex organ. The authors observe that the preserved structures of the syrinx and the position of Vegavis in the evolutionary tree are consistent with a capability to produce goose-like honks and other simple calls.
Given its fossilization potential, it is unclear why no other syrinx remains have been found in dinosaurs, but the authors propose that a complex syrinx may have been a late feature to arise in bird evolution, well after the origin of flight and improvements in respiration.