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'Missing link' fossil suggests birds ARE descended from dinosaurs after all

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Linda Dahlberg
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« on: June 22, 2009, 12:39:16 am »

'Missing link' fossil suggests birds ARE descended from dinosaurs after all

By Daily Mail Reporter
Last updated at 8:11 AM on 18th June 2009

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Fossil-hunters may have found the definitive 'missing link' between dinosaurs and birds, it was revealed today.

The creature is a small plant-eating dinosaur with a toothless beak, stunted arms, and unusual hands.

'Limusaurus inextricabilis' had key features that indicate a half-way point in the transition from dinosaurs to birds.
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Linda Dahlberg
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« Reply #1 on: June 22, 2009, 12:40:06 am »



Artist's impression of Limusaurus inextricabilis, which may be the definitive 'missing link' between dinosaurs and birds

Dinosaurs vanished from the face of the Earth at the end of the Cretace
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Linda Dahlberg
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« Reply #2 on: June 22, 2009, 12:40:14 am »

Dinosaurs vanished from the face of the Earth at the end of the Cretaceous period 65 million years ago. But some experts believe they live on as birds.

Evidence includes the fact two-legged theropod dinosaurs, such as Tyrannosaurus rex had bird-like feet, a bird-like pelvis, and a 'wishbone' typical of birds.

Like birds, they also had hollow bones that may have contained air sacs used in breathing. Some theropods are also believed to have sported primitive feathers.

In addition, preserved protein recently discovered in dinosaur bones appears to be structurally similar to that of modern chickens.

However, there are problems with the dino-bird theory.

Oregon State University recently the thigh bone, which is fixed in birds, stops their lung collapsing, allowing the breathing capacity for flight.

Every other animal that has walked on land, including humans and theropod dinosaurs had a moveable thigh bone.
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Linda Dahlberg
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« Reply #3 on: June 22, 2009, 12:40:40 am »



The fossil hand has key features that indicate a half-way point in the transition from dinosaurs to birds
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Linda Dahlberg
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« Reply #4 on: June 22, 2009, 12:40:55 am »

the bird hand, now reduced and embedded in the wing, does not look as if it was derived from a theropod dinosaur hand.

Birds and theropods seem to have retained a different selection of fingers from a five-fingered ancestor.

Until now scientists have believed that while theropods kept the first, second and third fingers, birds held onto the middle three fingers - the second, third and fourth digits.

If birds really are descended from theropod dinosaurs, this should not be the case.

But Limusaurus had hands different from those of any other theropod and may provide a solution to this part of the puzzle.

It had a shrunken first digit alongside more fully developed second, third and fourth fingers.
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Linda Dahlberg
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« Reply #5 on: June 22, 2009, 12:41:22 am »

Scientists believe the dinosaur was evolving towards having three-fingered hands resembling those of birds.

The find suggests that the three fingers of T. rex and other more advanced theropods are not digits one, two and three as had been assumed, but digits two, three and four - as in birds.

Dr Xu Xing, from the Chinese Academy of Science in Beijing, China, one of the experts whose description of Limusaurus appears today in the journal Nature, said: 'This discovery is truly exciting, as it changes what we thought we knew about the dinosaur hand.'

Limusaurus lived around 160 million years ago and was one of the most primitive members of a theropod group known as ceratosaurs.

Its skeleton was unearthed from a dinosaur 'mass grave' in the Gobi desert of north-west China.

The dinosaur was one of many that became trapped in an ancient mire pit and whose bones were later found stacked on top of each other. The treasure-trove of dinosaur fossils was featured in the 2008 National Geographic film 'Dino Death Trap'.

Besides its bird-like hands, Limusaurus had toothless beak-like jaws and short arms lacking sharp claws.

It also had gizzard stones similar to those used by birds to help them grind up tough plant foods.

The evidence points to Limusaurus being vegetarian, unlike most other theropods.

http://www.dailymail.co.uk/sciencetech/article-1193689/Missing-link-fossil-suggests-birds-ARE-descended-dinosaurs-all.html
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