The skeletal remains of Aurornis xui date to the Middle to Late Jurassic period.
Jonica Dos Remedios/Claude Desmedt/IRSNB
Skeleton and reconstruction of Aurornis xui, the world's oldest known bird.
A reconstruction of Aurornis xui, envisions the bird having grey-toned feathers, with distinctive markings on its wings and legs.
Textbooks around the world will need changing to reflect the oldest known bird. A new species has knocked Archaeopteryx out of its former top spot.
A small, feathered beast called Aurornis xui, described in the latest issue of Nature, is now believed to be the first known bird.
"Our analyses indicate it as the most primitive bird known,” said co-author Andrea Cau, a vertebrate paleontologist at the Museo Geologico Giovanni Capellini in Italy. "It was a small feathered dinosaur that lived in what is now China about 160 million years ago. It looked like a ground bird, but with a long tail, clawed hands and toothed jaws.”
Cau and colleagues recently analyzed the bird’s remains, which were unearthed at the Tiaojishan Formation of Liaoning Province in northeastern China.
The name Aurornis xui is made up of the words Aurora (Latin for "daybreak”) Ornis (Greek for "bird”) and xui, in honor of Xu Xing, a well-known Chinese paleontologist who specializes in feathered dinosaurs and the non-avian dinosaur-to-bird transition.
The line between non-avian dinosaurs and birds blurs at the mid-to-late Jurassic period, but the researchers believe that both Aurornis and Archaeopteryx were more bird than non-avian dino. Prior to this study, there was some debate over whether Archaeopteryx, which lived 10 to 15 million years after Aurornis, was a bird. The authors of this latest report believe it was.
There is now a clear lineage leading from non-avian dinosaurs to birds, starting with the clade of dinosaurs called Maniraptora ("hand snatchers").
"The maniraptoran theropods are the animals most similar to Archaeopteryx and early birds, and thus are the best candidate as avian ancestors,” Cau said. "In particular, we found that the earliest birds were very similar to the earliest troodontids, a kind of maniraptorans.”
The skeleton and reconstruction of Jonica Dos Remedios/Claude Desmedt/IRSNB
Troodontidae is a family of bird-like dinosaurs with feathers and two clawed limbs for movement on the ground. They had large eyes and laid eggs. This animal family is now thought to consist of the closest relatives of birds.
The study reveals that typical bird flight, powered only by the forelimbs, either evolved at least twice, or was subsequently lost or modified in some other species. It likely emerged when the earliest birds took to the trees.
"According to our scenario, powered flight evolved along the avian lineage after its separation from other maniraptorans,” Cau explained. "Powered flight probably evolved after early birds acquired more arboreal adaptations.”
The new fossils, combined with those of other early avians reveal that the earliest birds were widespread throughout Europe and Asia by the end of the Jurassic. The discovery supports what is seen today: a very far-reaching distribution of birds.
Paleontologist Michael Benton of the University of Bristol, commenting on the new paper, told Discovery News, "This is a very exciting new find from the pre-Archaeopteryx Tiaojishan Formation of China, and it appears to stabilize the phylogenetic tree.”
"Earlier suggestions of a more complex pattern of origin of birds were admittedly not robust, and the uncertainty in resolution was more statistical than real,” he continued. "It's interesting to see that the new specimen, Aurornis, can stabilize the result. The specimen is very good, complete, and shows a great deal of anatomical information.”
Benton concluded, "The new Chinese fossils confirm the classic pattern of relationships, with a tight sequence of fossils documenting the transition from dinosaur to bird.”