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Chinese scientists have unveiled more information about the dinosaur with the longest neck, Mamenchisaurus, dispelling the accepted view that the animal would have been able to raise its head like a giraffe.

Contrary to the fallacy that Mamenchisaurus could stride forward with its head held high, study on the neck bones of a well- preserved dinosaur revealed it could raise its head only slightly higher than the body within an angle of 20 degrees.

Doctor Ouyang Hui with the Chengdu University of Science and Engineering in Sichuan Province, in Southwest China, said if the head and neck span was 6.5 metres, the most comfortable head position would be within 2 metres above its body.

For the first time, scientists used computerized tomography scanning technology to study the head of a preserved dinosaur fossil, Mamenchisaurus youngi, and unveiled new information on its skull cavity size, shape and construction -- all rare stuff for dinosaur neurology.

The head contained 78 millilitres of brains, tiny compared to the huge body, but the brain had relatively advanced structural divisions.

Study of the sclerotic ring, a structure to adjust light into the eyes, indicated it had great eyesight.

When the dinosaur's teeth wore out, new ones grew at the same time in other cavities on the gum so it could continue to chew food, the research thesis showed.

A researcher with the United States once proposed that the neck of Mamenchisaurus was level instead of vertical to the body, reasoning the dinosaur needed a much stronger heart to support such a pose, but most people still likened them to giraffes, said Xu Xing, a researcher with the Institute of Vertebrate Paleontology and Paleoanthropology.

He Xinlu, the former vice-director of the China Society of Vertebrate Paleontology, said: "This is the first systematic research on Mamenchisaurus providing a lot of evidence and information.''

Mamenchisaurus was indigenous to East Asia and has been studied for half a century.

It was once the most famous dinosaur in China before the discovery of a feathered dinosaur in 1996, the thesis says. Previous opinions on the phylogenetic position of Mamenchisaurus varied because of the lack of reliable skull information and a complete description.

Mamenchisaurus youngi was unearthed in Xinmin County in Zigong in Sichuan Province in 1989. The specimen, 16 metres long with a 6.5 metre neck, is relatively small among various species of Mamenchisaurus, compared to the biggest one ever found in China spanning 35 metres.

Mamenchisaurus youngi, the best preserved specimen of Mamenchisaurus, helped scientists develop a detailed description of its complete skeleton framework, especially the skull, visual descriptions of the sclerotic ring and the fossilized skin of sauropods, which are rarely discovered, He said.

Mamenchisaurus fossils have been found exclusively in China in places like Sichuan Province and Yunnan Province in the southwest and in the Xinjiang Uygur Autonomous Region and Gansu Province in the nation's northwest.

The animals lived on foliage in the late Jurassic, about 150 million years ago.

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