Two extinct creatures were back in the news this week.

• Researchers in Montana have discovered what appear to be actual cells from a Tyrannosaurus rex leg bone.
• A magazine in Australia is offering a $1.25 million dollar reward for a living specimen of an
  extinct, wolf-like hunter called a Thylacine.

Of the two, the T. rex story is far more interesting, scientifically:

When [the scientists] got it into a lab and chemically removed the hard minerals, they found what looked like blood vessels, bone cells and perhaps even blood cells.
"They are transparent, they are flexible," said Mary Higby Schweitzer of North Carolina State University and Montana State University, who conducted the study.

Normally when an animal dies, its body decays quickly. Bones decay more slowly. In rare cases, the bones are buried and—if conditions are just right—as the bone decays it is replaced, molecule by molecule, with minerals. This results in a fossil--an exact replica of the original bone.

Sometimes the original body is preserved—if an animal is buried in ice, for example, or dies in an arid cave. But those specimens are never more than a few thousand years old. Insects trapped in amber may be tens of millions years old, but big animals? Never.

The idea that you could find actual tissue from a dinosaur was completely unexpected, and enormously exciting! Bones can only tell you so much. Soft tissue can tell us a tremendous amount about the animal's body and how it functioned. It might even help settle questions like were dinosaurs warm-blooded? And are they really close relatives of birds?

Of course, everyone wants to know if this will lead to Jurassic Park--taking DNA from dinosaur cells and using it to clone new dinos. That's pretty unlikely:

• Scientists still aren't sure if dinosaur tissue is what they've got here, let alone whether there is any DNA in it.
• Cloning technology is far from perfect. For every successful clone you read about, there are hundreds, even thousands of failures.
• DNA is a large, complex molecule that starts to break apart almost immediately after an animal dies. DNA from museum specimens only a few decades old is already unusable. DNA that's 70 millions years old isn't going to be any better.

So, we don't have to worry about any dinosaur petting zoos anytime soon!

(For more information, here's another news report.)

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