Sunday, August 9, 2009

Chicken a la Rex is a tasty find for researchers: Flesh of ancient predator and modern bird resemble each other at the protein level.(Science)BIOLOGY

T. rex was no chicken.

But scientists say soft tissue recovered from inside the leg bone of a 68-million-year-old Tyrannosaurus rex most closely resembles that of a modern hen.

This is the first time dinosaur protein has ever been sequenced. The feat, described in today's edition of the journal Science, means that researchers now have a new way to learn how ancient creatures are related to modern animals.

The discovery also bolsters the theory that birds descended from dinosaurs, and suggests that a T. rex drumstick might have tasted like chicken.

"What we knew, based on bone shape, was that dinosaurs are closely related to birds," said Mary Schweitzer of North Carolina State University and lead author on one of the Science papers.

"The similarity to chicken is definitely what we would expect."

The T. rex femur was discovered at the Hell Creek Formation in Montana in 2003, buried deep beneath the surface of a sandstone outcrop. Paleontologists had to break the leg into pieces to get it into the helicopter that was ferrying finds away from the site.

Dr. Schweitzer was able to isolate soft material from the hollow cavity of the bone. It seemed to contain blood vessels and cells.

At the time, many paleontologists believed this type of organic material couldn't survive for more than 100,000 years. When an animal dies, the protein in its body immediately starts to break down. In the case of fossils, the soft tissue is replaced by minerals, as bone turns to stone.

Dr. Schweitzer observed that the material was similar to tissue deposited inside hollow bones by modern birds when they are ovulating. Known as the medullary bone, it stays in place until the last egg is laid, and is then completely absorbed into the animal's body.

This means the T. rex was female, and was probably producing eggs when it died.

Dr. Schweitzer turned some of the material she extracted over to John Asara, a researcher at Harvard Medical School, who had developed a technique to identify the amino acids in protein fragments, both from human tumour cells and from mastodon bones 100,000 to 300,000 years old.

Amino acids are the basic components of proteins. Dr. Asara identified, or sequenced, the amino acids in protein fragments taken from the T. rex femur. He determined that some of it was a type of collagen.

Then he compared the dinosaur version with collagen found in modern chicken, newt and frog bones. Three of the protein fragments matched the chicken collagen. One fragment matched the protein from the newt, and another scrap was a match for the frog collagen.

"Most people believe that birds evolved from dinosaurs, but that's all based on the architecture of the bones," Dr. Asara said.

"This allows you to get the chance to say, 'Wait, they really are related because their sequences are related.' "

If researchers can find and sequence more proteins from T. rex and related dinosaurs, they should be able to glean more insight into how the ferocious carnivores gave rise to toothless grain-eaters like the modern chicken.

The mighty T. rex may have had some tiny, bird-like ancestors of its own. There is evidence it descended from a group of small, swift-bodied dinosaurs with a decidedly avian appearance. One was no bigger than a crow. Another resembled an ostrich.

The researchers did not sequence the DNA, or genetic material, of the T. rex, and Dr. Schweitzer said she may seek out collaborators to make the attempt. No one has ever successfully sequenced dinosaur DNA, she said. A number of attempts have been made, but the scientific community hasn't accepted any of the results.

Philip Currie at the University of Alberta said the work may change the way dinosaur hunters dig out bones.

Getting fossils out of the ground is hard physical work, often requiring bulldozers and dynamite.

But it's important that at least a portion of each specimen be left untouched and uncontaminated with glue or other material, he said. The hope is to extract proteins or genetic material back in the lab.

This is especially important when fossils are buried deep underground and protected from bacteria and surface water, said Jack Horner, the dinosaur hunter who found the T. rex femur in 2003. He is going to Mongolia and back to Montana to hunt for more exquisitely preserved fossils like the revealing T. rex.

"I don't think this is going to be unique in any way," he said.


Not quite birds of a feather

Tyrannosaurus rex

Weight: From five to 10 tonnes.

Height: Nine to 13 metres long.

Diet: They ate other dinosaurs, crunching their bones with the most powerful jaws in history.

Teeth: The size of bananas.

Eggs: Nobody knows, but eggs from a related dinosaur discovered in China were half a metre long.

Bones: Hollow and filled with air. Had a wishbone.


Weight: One to three kilograms.

Height: Roughly 30 centimetres.

Diet: Feeds on insects, larvae and seeds, occasionally indulging in cannibalism.

Eggs: 5.7 cm long.

Teeth: None.

Bones: Hollow and filled with air. Has a wishbone.


Source Citation:"Chicken a la Rex is a tasty find for researchers: Flesh of ancient predator and modern bird resemble each other at the protein level.(Science)(BIOLOGY)." Globe & Mail (Toronto, Canada) (April 13, 2007): A3. Popular Magazines. Gale. BROWARD COUNTY LIBRARY. 9 Aug. 2009

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