New facts not hard to swallow ( 2003-07-05 09:14) (China Daily)
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.
