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Fossilized Heart Offers Support For Dinosaurs as Warm Blooded

By Guy Gugliotta
THE WASHINGTON POST -- Scientists have found the first-ever fossilized dinosaur heart, and it appears to have four chambers, perhaps the strongest indication yet that dinosaurs were warmblooded animals, like birds and mammals.

The team of scientists used X-ray imaging to identify two ventricles and the hollowed-out cavity of a single aorta within a softball-sized mineral “concretion” removed from the skeleton of a Thescelosaurus. The pony-sized vegetarian dinosaur died about 66 million years ago in what is now northwest South Dakota.

The researchers said it was likely the animal’s two thin-walled auricles, or upper chambers, collapsed when it died, leaving the ventricles and the aorta as powerful evidence of a four-chambered heart, which in turn suggests a high metabolic rate, a prerequisite for any warmblooded animal.

“It’s very rare to get soft tissue that’s preserved,” said paleontologist Philip Currie of the Royal Tyrrell Museum in Alberta, Canada. “This is the first time for any evidence of a heart. It’s very exciting. If dinosaurs are warmblooded, they do indeed need four-chambered hearts.”

Investigation into the dinosaur heart was completed by a team of researchers from North Carolina State University, based on discovery of the dinosaur and initial research that began in 1993. The team’s findings were reported in the April 21 issue of the journal Science.

Despite a few remaining dissenters, paleontologists generally agree that dinosaurs were forerunners of modern birds, rather than reptiles. As this debate has waned, the search for evidence of warmbloodedness among dinosaurs has taken center stage.

Team member Dale Russell, an N.C. State paleontologist and curator of the North Carolina Museum of Natural Science where the fossil is displayed, explained that the key finding was not the heart itself but the single aorta.

“This means that low- and high-oxygen blood were separated,” Russell said, a signal that Thescelosaurus had much higher metabolism than reptiles, which have two aortas and mixed low- and high-oxygen blood.