Paleonews

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2009-04-03 – I Sauropodi “aspirapolvere” (Sauropods “vacuum cleaner”)

Uno studio di un iologo evoluzionista australiano pubblicato Biology letter supporta la teoria dei Sauropodi aspiravolvere. Secondo tale studio i sauropodi non potevano sollevare la testa (la pressione sanguigna da sopportare per inviare sangue al cerevello), tuttavia la loro stazza gli permetteva comunque di arrivare a raccogliere foglie da rami inaccessibili ad altri erbivori mentre il lungo collo gli permetteva di sostare in luogo e di agire appunto come un aspirapolvere agendo tutto intorno

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Sauropod dinos kept a level head

Anna Salleh
ABC

Long-necked sauropod dinosaurs would had to have used far too much energy to hold their neck upright and browse tall trees, says an Australian evolutionary biologist.

Dr Roger Seymour of the University of Adelaide reports his findings in the Royal Society journal Biology Letters.

Sauropods were about as heavy as a whale and had necks nearly five times the length of a giraffe’s.

The animals have generally been reconstructed with upright necks and it was assumed they grazed on tall trees.

But Seymour has calculated that to do this the dinosaurs would have needed to use 50% of the energy they consumed just to support their long necks.

“I think most people would agree that if you spent half of your energy pumping the blood around the body it would be an enormous cost,” says Seymour, who studies blood pressure in animals.

Seymour says the longer an animal’s neck, the higher the blood pressure it requires to pump blood to the brain.

“The giraffe’s blood pressure is twice that of other mammals,” he says.

While a human has a blood pressure of around 100 millimetres of mercury, a giraffe has a blood pressure of 200, says Seymour.

He says a sauropod with an upright 9-metre neck would have had to have a blood pressure of 700.

“That is exceptionally high,” says Seymour.

Seymour says to produce such a high pressure, the sauropod would need a heart with a 2-tonne left ventricle, which would be a challenge to fit in the animal.

And his most recent research has calculated that 50% of the energy it consumed would be used just to circulate the sauropod’s blood.

“Even though they may have had access to a larger amount of food, it would have cost more than the gain, basically,” says Seymour.

He says a giraffe with a 2-metre neck uses around 20% of its energy to circulate blood and humans use about 10%.

The ‘vacuum cleaner principle’

Previously, it was thought that sauropods must have been semi-aquatic or amphibious to support their enormous bulk.

When palaeontologists decided the animals were terrestrial, they assumed the neck was used like a giraffe’s, says Seymour.

But, he says, the sauropod’s enormous size meant the animal would have had many options for feeding even without having to lift their long neck vertically.

“Even without raising the head, these animals could browse higher than a giraffe,” says Seymour.

Seymour says feeding with a horizontal neck meant the animal could keep the bulk of its body in one place while using its long neck to graze in numerous places.

“It’s the vacuum cleaner principle,” he says.

source: http://www.abc.net.au/science/articles/2009/04/01/2530800.htm?site=science&topic=latest

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Other links:

Long-necked dinosaurs ‘kept their heads down’

Telegraph.co.uk – ‎1-apr-2009‎
Long-necked dinosaurs kept their heads down and did not raise them to the trees to graze, according to a new study. By Kate Devlin, Medical Correspondent

aprile 3, 2009 - Posted by | - R. Dinosauri, - Sauropodi, Articolo sc. di riferimento, Bl - Top posts, Italiano (riassunto), Lang. - Italiano, P - morfologia funzionale, P - Paleoetologia, Paleontology / Paleontologia, X - Riviste e Multimedia | , , , ,

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