University of Texas at Austin

Monday, December 21, 2009

Dinosaur facts and fantasy

Tawa, ready for its close-up

Tawa, ready for its close-up

Listening to Sterling Nesbitt talk about Tawa hallae, the 215 million-year-old dinosaur that he and his colleagues wrote about in the Dec. 17, 2009 edition of Science, I was struck when he used the word “fantasy.”

Dinosaurs and fantasy are not strangers. From the imaginations of children enthralled by dinosaurs to Steven Spielberg’s special effects, our images of dinosaurs often exceed reality.

But really, how real can scientists be when talking about creatures that lived millions of years ago?

Scientists can get pretty real, especially when fossils are as well preserved as Tawa’s were.

Fantasy is employed in trying to figure out what the dinosaur looked like from the outside.

Sterling Nesbitt

Sterling Nesbitt

Nesbitt, a post-doctoral researcher at the Jackson School of Geosciences, called Tawa’s preservation so “exquisite” that “we can essentially have each bone in three dimensions.”

Webcast with Nesbitt

Not only could the paleontologists tell that it walked on two legs and that it ate meat (with its sharp claws and teeth, it ate pretty much whatever it wanted), but how certain joints fit together in a very precise way and what the wear and tear on the bones meant.

“So it gives us new information about the origin and early evolution of dinosaurs,” Nesbitt said.

That’s very similar to the way John Kappelman, an anthropology professor who studies human origins, talks about hominid fossils and how the smallest details can be telling.

Tawa's right hand, an example of the exquisite preservation

Tawa's right hand, an example of the exquisite preservation

But no matter how well the bones are preserved, the dinosaur’s soft tissue is long gone.

That’s where a dash of fantasy is added to well-grounded reality comes in.

“We try to use what we know about birds and crocodilians (closest living relatives of dinos), when reconstructing the soft tissues of dinosaurs,” Nesbitt said. “However, birds and crocs are very different so it leaves lots of guess work.”

He said the presences of integumentary structures (body covering such as skin, feathers and scales) occur in ornithischian dinosaurs (relatives of Triceratops) and in many theropods (carnivorous dinosaurs).

“Because both groups of dinosaurs have a covering, we can posit that their common ancestor had similar structures,” Nesbitt said. “So, Tawa, a theropod dinosaur, also had some kind of covering.”

Such inferences go only so far.

“Some of it is fantasy,” he added. “It is a reconstruction because, of course, the soft tissues are not preserved with these specimens.”
But fantasy is not for scientists. It’s for those of us who want a dinosaur with personality.

“The science is in the bones,” Nesbitt says. “The reconstruction is for education purposes.”

More images, animations and videos are available online.

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