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A 100-million-year-old fossil of an Ichthyornis shows how birds evolved beaks - News Techcology скачать в хорошем качестве

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A 100-million-year-old fossil of an Ichthyornis shows how birds evolved beaks  - News Techcology
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A 100-million-year-old fossil of an Ichthyornis shows how birds evolved beaks - News Techcology

A 100-million-year-old fossil of an Ichthyornis shows how birds evolved beaks - News Techcology Newly uncovered fossils of a toothed seagull-sized bird represent a pivotal moment in the transition from dinosaurs to modern-day avians, experts say.A rare fossil of Ichthyornis dispar, which lived in North America around 100 million years ago, has revealed that the first bird beaks had teeth.Unlike most preserved remains of ancient creatures, which present a flat cross section, researchers discovered an I. dispar skull fossilised in three dimensions.They used advanced CT imaging scans to shed light on how the creatures, which arose in what is now North America, were a stepping stone to modern beaks.The feature they discovered was a 'horn-covered pincer tip' with teeth, which would become the bird beak were are now familiar with.A team led by scientists from the universities of Bath and Yale discovered the complete skull, as well as two previously overlooked cranial elements that were part of an original specimen housed at Yale since the 1870s.In modern birds, the beak is made up of a small region called the maxilla and a larger area called the pre-maxilla.In contrast, the beaks of dinosaur-like early birds such as Archaeopteryx, which lived 150 million years ago, were mostly made up of the maxilla.The skull of I. dispar was found to be a cross between the two and its beak had a large maxilla with teeth and small pre-maxilla.About the findings, Dr Daniel Field, from the University of Bath, said: 'The fossil record provides our only direct evidence of the evolutionary transformations that have given rise to modern forms,'Most fossils are squashed flat during the fossilisation process, making it almost impossible to study the anatomy of the brain and details of the skull.'This extraordinary new specimen reveals similar brain proportions to that of a modern bird, but other parts of the skull more closely resemble the skulls of predatory dinosaurs.'Both birds and reptiles descended from archosaurs, who dominated the Earth around 250 million years ago.Archosaurs gave rise to the age of the dinosaurs and, eventually, birds and reptiles as their only living descendants.Fossils are normally created when creatures bodies come to rest on the bottom of fossil beds, generally the bottom of bodies of water. They are then squashed by the accumulated layers of sand and other sediment.In the case of 3D fossils, these animals were victims to an avalanche of sand and water, with the fossils caught up in the middle. This means they are preserved within the rock, rather than flattened against it.One difference found with the 3D Ichthyornis skull was that the cheek region was bounded by the bones of the skull roof and side of the skull. This trait is more like a dinosaur head.Researchers conclude that key features of the brain and palate evolved before the jaw muscles.The research also revealed that the feeding apparatus of living birds evolved earlier than previously thought.Study corresponding author Assistant Professor Bhart-Anjan Bhullar, a paleontologist at Yal Source: http://www.dailymail.co.uk/sciencetec...

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