A Dino Locked Inside A Bird Skull

AsianScientist (Jan. 25, 2022) – There’s more to a tiny bird’s head than meets the eye, with its unique skeleton providing further clues to the links between living birds and ancient dinosaurs. Reporting in Nature Communications, researchers discovered a fossilized skull presenting a mix of dinosaur and bird features from Liaoning province in China.

While the era of the dinosaurs may long be over, scientists continue to dig up clues about the awe-inspiring beings that once walked the planet. By piecing together lines of evidence from fossils, they have been able to decipher how dinosaurs lived and pinpoint certain features that may have been preserved or evolved into a varied set of characteristics seen in almost all creatures around us today.

During the Cretaceous period, the last stretch of time before the dinosaurs were wiped out, a diverse but now extinct group of birds called enantiornithines roamed all over the ancient earth. They differed from modern birds because they had locked up temporal bones, which form the side walls of the skull, making the coordination between the upper and lower jaw restricted. In contrast, living birds have a ‘kinetic skull’ that allows the upper jaw to move independently of the lower jaw.

The 120-million-year-old enantiornithine fossil skeleton uncovered by Dr. Wang Ming and colleagues at the Chinese Academy of Sciences resembled the skull of dinosaurs like Tyrannosaurus rex. The bird fossil had two bony arches at the back of the skull, reinforcing its rigid or locked up state—much like reptiles such as lizards and alligators.

Another bone, which the team proposed to be the pterygoid where muscles for chewing are attached, looked exactly like that of Linheraptor, a dinosaur relative linked with living birds. Alongside the locked up temporal bones, the lack of direct contact between the pterygoid and palate bones also provided new evidence on the lack of kinesis or movement among early birds’ skulls.

The researchers suggested that the immovable jaw may have affected enantiornithines’ survival approaches during the Cretaceous period, imposing dietary constraints. That limitation likely became an evolutionary driving force favoring kinetic skulls in modern birds.

The team’s finding marks the discovery of the first well-preserved pterygoid bone in an early bird. By keeping many of the features of dinosaurs, this structure indicated that early birds’ skulls had similar functions to that of their dinosaur ancestors than today’s living birds.

Moreover, the expansion of the enantiornithines family tree with this new bird species further supports the idea that birds are not only living dinousaurs but are modern creatures that evolved from a specific group of dinosaurs including the likes of the Linheraptor and well-known Velociraptor.

“Having a ‘dinosaur’ skull on a bird body certainly did not stop the enantiornithines, or other early birds, from being highly successful in places all around the world for tens of millions of years during the Cretaceous,” said Wang.

The article can be found at: Wang et al. (2021) Cretaceous Bird With Dinosaur Skull Sheds Light on Avian Cranial Evolution.

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Source: Chinese Academy of Sciences; Photo: Wang Ming.
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