CHICAGO, Ill. — A lost world of spectacular prehistoric birds has been discovered near the Great Wall of China. Researchers at Chicago’s Field Museum say the fossilized bones provide new insights into the evolution of our feathered friends.
One newly discovered species had small, closely packed peg-like teeth and a moveable pincer-like chin. Study authors call it Brevidentavis zhangi, which translates to “short-toothed bird.” Another, called Meemannavis ductrix, appears to be a toothless creature, like its modern descendants.
A team discovered the treasure trove at an ancient graveyard at Changma, 80 miles from the wall’s western most reach. It includes more than 100 specimens of creatures that lived 120 million years ago, during the time of the dinosaurs.
An international team analyzed skulls and necks from six of these fossils and identified the flexible bony appendage at the tip of Brevidentavis’ lower jaw. The adornment, known as a predentary, was also highly sensitive — suggesting the bird used it to hunt prey.
“Brevidentavis is an ornithuromorph bird with teeth, and in ornithuromorphs with teeth, there’s a little bone at the front of the jaw called the predentary, where its chin would be if birds had chins,” explains lead author Professor Jingmai O’Connor, curator of vertebrate paleontology at the Field Museum, in a media release.
Discovering an ancestor of modern birds
Previous scans of another fossil bird revealed that it underwent stress and also identified cartilage that only forms when there is movement.
“In this earlier study, we were able to tell that the predentary was capable of being moved, and that it would have been innervated – Brevidentavis wouldn’t just have been able to move its predentary, it would have been able to feel through it,” Prof. O’Connor says.
“It could have helped them detect prey. We can hypothesize that these toothed birds had little beaks with some kind of movable pincer at the tip of their jaws in front of the teeth.”
The discoveries add to our understanding of prehistoric bird diversity, especially in the Changma region — about 1,200 miles west of Beijing. Other specimens examined belong to Gansus yumenensis, the oldest known member of the group that includes modern birds.
“Gansus is the first known true Mesozoic bird in the world, as Archaeopteryx is more dinosaur-like, and now we know what its skull looks like after about 40 years,” says co-author Prof. Hai-Lu You from the Chinese Academy of Sciences.
Archaeopteryx lived around 150 million years ago and scientists call it the “world’s first bird.” However, this creature is actually an intermediate step in evolution between the birds we see flying around today and predatory dinosaurs like Deinonychus. The raven sized creature had feathers on its legs and wings and could fly short distances, a bit like a pheasant.
“These amazing fossils are like a lockpick allowing us to open the door to greater knowledge of the evolutionary history of the skull in close relatives of living birds,” says co-author Prof. Tom Stidham, also from the Chinese Academy of Sciences.
“At a time when giant dinosaurs still roamed the land, these birds were the products of evolution experimenting with different lifestyles in the water, in the air, and on land, and with different diets as we can see in some species having or lacking teeth. Very few fossils of this geological age provide the level of anatomical detail that we can see in these ancient bird skulls.”
Finding teeth ‘never seen in any other dinosaurs’
The study in the Journal of Systematics and Evolution is the culmination of excavations at the site in northwest China over the last two decades. Unfortunately, many of these fossils are incomplete and badly crushed, making them difficult to classify.
“It was a long, painstaking process teasing out what these things were,” Prof. O’Connor continues. “But these new specimens include two new species that increase our knowledge of Cretaceous bird faunas, and we found combinations of dental features that we’ve never seen in any other dinosaurs.”
Study authors explain that all birds are dinosaurs, but not all dinosaurs are birds. A small group evolved into birds. They co-existed for 90 million years. Modern birds are the descendants of the group that survived the asteroid strike that wiped out the dinosaurs and many prehistoric birds.
Prof. O’Connor’s work focuses on studying different groups of early birds to figure out why some survived.
“These fossils come from a site in China that has produced fossils of birds that are pretty darned close to modern birds, but all the bird fossils described thus far haven’t had skulls preserved with the bodies,” adds co-author Prof. Jerry Harris from Utah Tech University. “These new skull specimens help fill in that gap in our knowledge of the birds from this site and of bird evolution as a whole.”
Changma is a prehistoric treasure chest
“The Changma site is a special place,” says co-author Dr. Matt Lamanna of Pittsburgh’s Carnegie Museum of Natural History. “The fossil-bearing rocks there tend to split into thin sheets along ancient bedding planes. So, when you’re digging, it’s like you’re literally turning back the pages of history, layer by layer uncovering animals and plants that haven’t seen the light of day in roughly 120 million years.”
Through painstaking work, the researchers were able to identify key features in the birds’ jaws that showed two of the six specimens were unknown to science.
“Because the specimens were pretty flattened, CT-scanning them and fully segmenting them could take years and might not even give you that much information, because these thin bones are flattened into almost the same plane, and then it just becomes almost impossible to figure out where the boundaries of these bones are,” O’Connor concludes. “So we had to kind of work with what was exposed.”
South West News Service writer Mark Waghorn contributed to this report.