Artist’s reconstruction of Janavis finalidens, a really massive marine chicken from the late Cretaceous. In the background are Asteriornis, one other chicken present in the identical fossil deposit Phillip Krzeminski
A 67-million-year-old chicken cranium has overturned a longtime principle about how trendy birds advanced.
Unlike most trendy birds, the flightless group that features ostriches and emus can’t transfer their higher beaks – a characteristic that, for the previous 155 years, has been thought of primitive. The discovery of a jointed higher beak in a chicken from the dinosaur age, nevertheless, means that the early ancestor of all trendy birds might have had a jaw that seemed extra like that of a turkey than an ostrich, says Daniel Field on the University of Cambridge.
“The assumption that ostriches, rheas, emus and kiwis somehow retain features that are indicative of what the ancestor of modern birds might have been like – I think that’s actually just not right,” he says. “I always assumed that it was, but I don’t buy it anymore.”
In 1867, biologist Thomas Henry Huxley proposed that birds with fused higher beaks had maintained this trait from historic ancestors, and that jointed higher beaks – which permit the highest beak to maneuver up and down independently of the top – advanced later. Approximately 99 per cent of recent birds have jointed higher beaks, which can have benefits for nest-building, grooming, food-gathering and defence, says Field.
About 20 years in the past, researchers on the Natural History Museum of Maastricht, within the Netherlands, analysed a fossil partially encased in stone which had been discovered by a collector close to Liège, Belgium. The group recognized one of many protruding bones as a shoulder bone and believed that there have been cranium bones trapped contained in the stone. They additionally discovered a tooth.
Then in 2018, Juan Benito, additionally on the University of Cambridge, borrowed the specimen from Maastricht. He was keen to review a fossil which may include historic chicken cranium bones, since they’re so delicate that they not often fossilise. To his disappointment, nevertheless, CT scanning revealed that the suspected cranium bones have been truly “just a bunch of vertebrae and ribs”, he says.
The rock containing the Janavis fossils Dr Juan Benito and Dr Daniel Field, University of Cambridge
Two years later, Benito took one other have a look at that so-called shoulder bone and thought it seemed unusual. He contacted Field and collectively they created 3D scans of that and one other protruding bone that gave the impression to be mislabelled.
To their amazement, the 2 bone items matched up completely alongside their fragmented strains. Combined, they created a single bone that seemed lots just like the jointed higher beak bone of most trendy birds, known as the pterygoid.
Comparisons of their scans with these of 34 different fossilised birds and dozens of recent birds confirmed the bone’s id and prompt that, like trendy turkeys and geese – and in contrast to ostriches, emus and rheas – this historic chicken may carry its higher beak.
It would have been weighed about 1.5 kilograms – just like a gray heron or turkey vulture, says Benito. The group named it Janavis finalidens, for Janus, the Roman god of beginnings and endings, and for the Latin phrases avis, finalis and dens, which imply chicken, ultimate and enamel.
Janavis finalidens was one of many final recognized toothed birds, that are suspected to have died out throughout the mass extinction of dinosaurs 66 million years in the past.
The findings counsel that, surprisingly, ostriches and their family will need to have advanced a fused beak later, says Lawrence Witmer at Ohio University, who wasn’t concerned within the examine. “We always thought the palatal structure of ratites was primitive and dinosaur-like,” he says. “This new study is a remarkable example of how just a few key fossil remains – analysed with a keen eye – can overturn some longstanding and cherished notions.”
The discovery completes one other puzzle as effectively. Last yr, Chris Torres, now at Ohio University, and his colleagues pieced collectively practically your complete skeleton of a million-year-old chicken known as an Ichthyornis, however they have been lacking one vital bone within the beak. When Benito and Field scaled down their pterygoid to the relative measurement of the chicken, the bone match completely.
“We hypothesised that a… mobile palate must have been present in the ancestor of living birds, but that skull was missing the one bone that would have really closed the case,” says Torres. “Imagine my shock when, just over a year later, Juan, Dan and colleagues come along with that very bone from [a similar species] and it fits perfectly!”
Journal reference: Nature, DOI: 10.1038/s41586-022-05445-y
More on these matters: