In the vast majority of birds, both parts of the beak – the upper (maxillary) and lower (mandibles) – move independently of the skull. In 1867, biologist Thomas Henry Huxley hypothesized that birds whose upper beaks do not move independently inherited this trait from their ancestors. The independently moving parts of the beak would have evolved later, as they provide an advantage when it comes to foraging, building a nest, defending themselves, or raising chicks.
British German Expert Group Analyze it Preserved jawbones of the beak of the great prehistoric bird they named final janavis. It lived at the end of the dinosaur era and was one of the last birds to have teeth. Beak bone arrangement J final indicates that it was quite mobile, and in this respect almost indistinguishable from the beaks of modern birds. This discovery changes our understanding of the evolution of this group of animals. Until now, it was thought that a fully mobile beak, with both parts moving independently of the skull, evolved only after the dinosaurs became extinct.
All currently living bird species can be classified in terms of jaw structure into one of two subclasses. Archaic (“archaic-jawed”) birds include, for example, ostriches and kiwis, whose jaws do not move. All the rest are neognathic (“having new jaws”).
In the 1990s, a fossil dating back to 66.7 million years was found on the Dutch-Belgian border. It was first studied in 2002. At that time, scientists could only describe what they saw from the outside. Almost 20 years later, the fossil was borrowed by Dr. Daniel Field from the University of Cambridge’s Department of Earth Sciences. He and his colleagues set out to study it with the latest tools. The scientists used a CT scanner.
“We had high expectations. It was originally described as having skull fragments which are often not preserved. However, the CT scan showed nothing that looked like part of a skull, so we gave up, says Dr. Juan Benito, who was working on his PhD at the time. Then came the pandemic and the lockdown. So Benito decided to take another look at the fossil.
The previous description is meaningless. There was a greatness I could not describe. It was described as an arm bone, but I didn’t understand how that was possible. He shared his suspicions with Field. It wasn’t actually an arm bone, but it reminded him of something, said Field, curator of the ornithology collection at the University of Cambridge’s Zoological Museum.
We realized we’d seen a similar bone in a turkey’s skull. We just had skulls like this in our lab. We took one, we compared the bones, and they were almost identical,” says Benito. This proves that the movable lower jaw appeared in birds even before the extinction of the dinosaurs. Moreover, it is also evidence that the non-moving lower jaw of ostriches and their relatives evolved after the appearance of the lower jaw mobile.
The main features that distinguish birds from their ancestors are the lack of teeth and a movable jaw. if final janavis He had teeth, so he wasn’t modern in that respect, he also had a modern, movable lower jaw.
The researchers also showed the shape of the bone that was examined J final It is more like the similar bone in chickens and ducks, and less so in ostriches and their relatives. Evolution does not follow straight lines. This fossil shows that the fully mobile beak, a trait we attribute only to modern birds, evolved before they appeared. We’ve been wrong for more than a century, says Field.
Dr.. Joan Benito, Dr. Daniel Field, University of Cambridge / Knowledge Mine
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