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June 03, 2005

More About That Dinosaur Soft Tissue

A couple of months ago (in a post now inaccessible since I reinstalled Movable Type) I posted a story about some paleontologists who'd found the fossilised remains of a T. rex and discovered, on cutting open a thigh bone, that it contained unfossilised soft tissue. Which was gobsmacking enough.

Now, a follow-up piece: read on!

Dinosaur bones show T. rex link to birds

By Maggie Fox, Health and Science Correspondent Thu Jun 2, 2:02 PM ET

WASHINGTON (Reuters) - A Tyrannosaurus rex dinosaur that died 68 million years ago has provided some of the strongest evidence yet that birds are the closest-living relatives of dinosaurs, scientists said on Thursday.

Soft tissue found in the animal's thighbone strongly suggests it was a female, and just about to lay eggs, the researchers report.

The bone tissue is strongly similar to that made inside the bones of female birds -- and no other living type of animal -- when they are producing the hard shells of eggs just before they lay them, said Mary Higby Schweitzer of North Carolina State University in Raleigh.

"In addition to demonstrating gender, it also links the reproductive physiology of dinosaurs to birds very closely. It indicates that dinosaurs produced and shelled their eggs much more like modern birds than like modern crocodiles," Schweitzer told reporters in a telephone briefing.

Female birds produce a layer of bone tissue called medullary bone when they are laying eggs. It is rich in calcium, providing minerals that would otherwise be leached from harder bone material, leaving the bird susceptible to fractures.

"The way that crocodiles lay and shell their eggs is they hold them in their reproductive tract and shell them all at once," Schweitzer said.

"Birds shell their eggs one at a time as they move down through the reproductive tract. It is a pretty calcium-intensive process."

ALREADY A STAR

This particular T. rex fossil made headlines in March when the same team of paleontologists reported it contained preserved soft tissue -- the first ever found in a dinosaur bone.

"The reason that we have found all the things in this one particular animal is this specimen was in a very remote part of Montana, in the Hell Creek formation," said Jack Horner of the Museum of the Rockies and Montana State University.

"It was so far out in the country that we needed to helicopter it out and we actually had to split the thighbone into two pieces to get it into the helicopter."

When Schweitzer unwrapped the cracked-open femur she immediately saw the soft tissue and went to work proving its remarkable state of preservation.

Horner plans to crack open some other bones.

"We have 12 specimens of Tyrannosaurus rex here at this institution, and we are about to find out if any more of them are females, just by looking inside," he said.

It was a stroke of luck to find an animal at just the right stage to be making medullary bone, Schweitzer said.

"It would not be present in a brooding animal," she said.

"But it would be present as long as there was an egg left to lay. The animal was probably near the end of its laying cycle."

Finding another such specimen will be difficult.

"I think it is pretty much a long shot," she said.

In April, Tamaki Sato of the Canadian Museum of Nature in Ottawa, and colleagues reported they had found the fossil of a dinosaur in China that carried two eggs in its body.

Its physiology also was closer to modern birds than to modern crocodiles, Sato reported.

Horner said most experts are convinced the two-legged dinosaurs known as theropods were closely related to living birds.

"This is another piece to the puzzle and there are a lot of them," he said. "Anyone who would argue that birds and dinosaurs are not related -- frankly I'd put them in the Flat Earth Society group."

Posted by adrian at June 3, 2005 09:28 PM

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