Fad dieting wasnāt an option in the Cretaceous, so the earliest birds went to more extreme measures to address weight issues: they lost their teeth.
Archaeopteryx, at 150 million years old still the oldest known bird, had an imposing set of teeth. But within 20 million years, at least some birds were toothless. Now a team led by Zhonghe Zhou at the Chinese Academy of Sciences in Beijing believe they know why.
They discovered Zhongjianornis yangi, a toothless bird from 122 million years ago in Chinaās Liaoning province. Their analysis shows that “Ü.Ģż²ā²¹²Ō²µ¾± belonged to one of four bird groups that independently lost their teeth, implying that this loss was no evolutionary fluke. “Ü.Ģż²ā²¹²Ō²µ¾±ās group is the most primitive among them, suggesting it could provide clues as to why tooth loss occurred.
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The team compared the body structure of a number of early birds and found that some toothed species were more adapted for flight. They think natural selection may have put pressure on weaker fliers to lose their teeth in a bid to improve their skills by losing excess weight. āIt would be especially advantageous to reduce the weight of the head because [it] is further from the centre of gravity,ā they write.
That theory is āas good as any otherā, says at the University of Bristol, UK, though he remains sceptical. āLosing teeth wouldnāt make a huge difference to balance in the air.ā
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