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A Heart of Stone

It was 103°F in hell creek, South Dakota, in September of 1993. Michael Hammer, a professional fossil preparer, was digging out a T. rex in the hot sun. "We were roasting and toasting," he recalls, when he turned his attention to the nearby remains of a plant eater, a dinosaur called Thescelosaurus. Heavy rains had washed away so much silt that much of the 13-foot skeleton lay exposed. "I looked down and my heart started palpitating," Hammer says. "This animal has been known before but not with a skull. I knew I had a very special specimen."

Just how special was finally revealed last week in a report in the journal Science. The Thescelosaurus skeleton not only survived 66 million years with virtually every bone intact, but inside its chest cavity was what seemed to be a fossilized heart--the first dinosaur heart ever seen.

The reddish-brown, grapefruit-size stone was examined at Ashland Hospital in Oregon and then sent to North Carolina State University, where experts used a computer to construct a 3-D image. Says imaging expert Paul Fisher: "It became very apparent that, yeah--this was the real deal."

The heart's structure challenges some basic ideas about dinosaurs. It appears to have four chambers, with a single main artery, or aorta, entering it. So it is "more like the heart of a mammal or a bird than a reptile," says paleontologist Dale Russell. This finding adds to the growing body of evidence that dinosaurs were warm-blooded and could maintain a constant body temperature. Warm-blooded animals tend to be more energetic and active than cold-blooded ones, like snakes.

Other experts will have to study the fossil to confirm the heart finding. But one thing is clear, says paleontologist Mark Norell of the American Museum of Natural History--digital-imaging equipment is opening new windows on the past: "We're starting to see a lot more wild stuff. It's an exciting time."

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