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OnCampus Weekly.. Oct. 31/03

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donald hendersonFloating dinosaur theory holds water

U of C paleontologist studies buoyancy
of sauropods

by NSERC Newsbureau

They were the biggest animals ever to walk the earth. And now the giant sauropod dinosaurs – known as “long-necks” to millions of kids – have another claim to fame. They were also the largest to ever float.

“ The sauropod dinosaurs were the colossal corks of the Mesozoic,” says Donald Henderson (right), a postdoctoral researcher at the U of C who teaches biology and conducts research with Faculty of Science professor Anthony Russell.

Henderson presented his NSERC-funded discovery this month at the annual meeting of the Society of Vertebrate Paleontology in St. Paul, Minnesota.

While it’s well known that many modern large animals can swim, sauropods have long been viewed as bulky leviathans in a class of their own. These giants tipped the scales at between 10 and 30 tonnes and were up to 30 metres long and 12 metres in height.

Scientists initially thought they were swamp waders, too huge to have survived on land without crushing themselves. In the 1950s, the theory changed; some thought a submerged sauropod would be covered with water to such a depth that the water pressure wouldn’t allow it to expand its lungs.

Recently, evidence appeared that these heavyweights had bird-like lungs and air sacs. Modern birds have a series of balloon-like air sacs in their bodies that reduce their weight and aid respiration.

Research on sauropod vertebrae found the telltale marks of bird-like air sacs. Scientists now think that sauropods were full of air – at least 15 percent of their body volume was air sacs.

“ Using 3-D computer modeling, I found that when you give sauropods bird-like lung systems and air sacs they’re actually really light . . . so they float really high in the water,” Henderson says.

He made the startling discovery using 3-D mathematical and computer models of animal buoyancy.

The computer modeling also indicates sauropods had a centre of balance above their centre of buoyancy and so would have been very unstable once afloat.

“ If they lost contact with the bottom they would tip sideways and be in serious trouble,” he says.



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