66.7 million years ago, a flat sea covered parts of today's Belgium, the climate resembled tropical beaches as on the Bahamas. Janavi's final lived there, a very large sea bird with long wings and teeth in the jaw, which chased fishing or ink fishing in the water. Fossil remains of one of these tooth birds are probably throwing common ideas about the evolution of modern birds. This is suggested by a study in "Nature" that a working group around Daniel Field from the University of Cambridge presented.
With the help of CT recordings, the team examined petrified fragments of a skull of the tooth bird and encountered characteristics that was not actually expected in this bird line. Accordingly, the movable beak - the main feature of the skull of 99 percent of modern bird species - has already developed before the mass extinction at the end of the chalk season. At that time, 66 million years ago, many other animal and plant families disappeared in addition to the dinosaurs. For more than 100 years, biologists had assumed that this peculiarity only developed after that catastrophe.
Only the small group of flightless ratites such as ostrich, emu or nandu cannot move their upper beak half, which is why they are considered primitive. They belong to the Palaeognathae or primitive jawbirds, while the great majority of all other bird species belong to the new jawbirds or neognathae, which have a mobile palate. The two groups were originally classified by Thomas Huxley, who was particularly vocal in his support of Charles Darwin's theory of evolution. In 1867, he divided all living birds into either the "ancient" or the "modern" groups of pines. The Briton assumed that the "old" jaw shape was the original state of modern birds, and the "modern" jaw developed only later.
The more precise analysis of the old skull bone refutes this. He was found in the 1990s and for the first time in 2002. At that time, the scientists could only rely on what they could see from the outside. They described the pieces of bone that protruded from the rock as fragments of skull and shoulder bones and brought the otherwise inconspicuous-looking fossil back into the fund. Almost 20 years later, it finally came to Juan Benito to Cambridge, who finally examined the find as part of his doctoral thesis with a computer tomographer and recognized the true value.
However, this was only possible at second glance. "The previous descriptions of the fossil simply did not make sense. There was a bone that really puzzled me. I could not understand how what was first described as a shoulder bone could actually be a shoulder bone, " says the paleontologist. Together with Field, he finally realized what it was actually about: "Then we realized that we had seen a similar bone before – in a turkey skull." A comparison of both bones finally showed that both were virtually identical.
From this, the researchers conclude that the modern jaw, as turkey and many others have, could have developed in front of the "old", stars of the ostriches and their relatives. For an still unknown reason, the merged culinary bones of the running birds must have developed at a time when modern birds were already established - or their ancestors from the dino period have not yet been found. Non -bird -like dinosaurs such as the tyrannosaurs also had a merged palate.
Janavis finalidens, on the other hand, illustrates the transition from the dinosaur ancestors of birds: although he still had teeth and is therefore a pre-modern bird, but his jaw structure already corresponded to that of his modern relatives. This finding does not mean that one has to rewrite the entire bird family tree, according to the working group. However, it redefines our understanding of an important evolutionary feature of modern birds.
Like the big dinosaurs and other tooth birds, Janavis did not survive the chicxulub impact at the end of the chalk, possibly because it was relatively large. The bird weighed about 1.5 kilograms and had the dimensions of a today's Geier. With these dimensions, many animal species were at a disadvantage, while smaller species survived, including the "wonder chicken", which came from the same area in 2020 and existed next to Janavis. The miracle chicken is considered the oldest known specimen of a modern bird.
