Palaeontologists working about 130km from the Great Wall of China announced last Friday (Feb 18) the discovery of two new species of birds that lived alongside the dinosaurs around 120 million years ago.
One of the birds, named Brevidentavis zhangi, featured a pincer-like appendage on its lower jaw covered in keratin, the type of protein that makes up our skin and nails. The scientists hypothesised it could have been used for hunting.
Jingmai O'Connor, the lead author of the study and associate curator of vertebrate palaeontology at Chicago's Field Museum, said the appendage could have helped the birds detect prey.
Unlike modern birds, the Brevidentavis also had teeth, which were small and packed closely together in the beak.
"These birds with predentaries (a bone in the lower jaw) had jaws full of teeth except the tip of the jaws, which had a little beak. The lower half of the beak at the tip, formed by the predentary, could move slightly up and down, helping to grip food with a pincer-like movement," she said.
O’Connor pointed out that predentaries can be difficult to imagine because the ability to 'feel' through the jaw is alien to humans.
"They could probably detect subtle pressure changes in the water that would indicate movement and that prey is nearby. Living birds can do this with something called the bill tip organ, in which sensory cells are clustered at the tip of their beak. Crocs can also do this with special scales on their bodies," she said.
The other fossil, named Meemannavis ductrix, was toothless, like modern birds. It was named after Meemann Chang, a Chinese palaeontologist who was the first woman to lead the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing. She was the director between 1983 and 1990.
The team found only skulls of the two new species, so the birds could have other unknown anatomical features.
Both birds are part of a group called ornithuromorphs, which includes all modern birds and many of their extinct relatives.
O'Connor said some prehistoric birds had some anatomical differences from modern birds, such as the teeth, but the behaviour of ornithuromorphs would have been so similar to today's birds that it would probably be indistinguishable to untrained eyes.
"They had colourful feathers and eggs, incubated their eggs, some had ornamental plumage in males that probably courted females — but these are all features that birds (avian dinosaurs) inherited from non-avian dinosaurs. So, dinosaurs closely related to birds did all these things too," she said.
The study pointed out that all birds are dinosaurs, but not all dinosaurs are birds. The species unearthed in Gansu would have been part of a small number of dinosaurs that had evolved into birds and lived alongside dinosaurs for 90 million years.
The scientists found six different types of birds when they excavated the Changma palaeontology region in Gansu province in northwestern China. The majority of the fossils at the dig site belonged to a species called Gansus yumenensis, which were first discovered in 1981.
O'Connor said finding fossil sites help add a piece to tell the very long story of evolutionary history. She said trying to answer questions like, "Why were the Gansus grouped in such large numbers at this site?" could help us understand more about modern colonial nesting birds like egrets.
"We are trying to use these few puzzle pieces we have to understand something as complex as the evolution of all vertebrate life culminating in all the groups we see alive today and the many that went extinct along the way," she said.
This article was first published in South China Morning Post.