Dinosaur Crest Debate Runs Hot and Cold

A 4-foot-long crest protruding from a fossil dinosaur skull found in the badlands of northwestern New Mexico is prodding paleontologists in their debate over the creature’s body temperature.

“It looks like there was a lot of heat exchange going on with this crest. To me, that suggests it was coldblooded,” said Tom Williamson, a New Mexico Museum of Natural History paleontologist who led the expedition team that found the Parasaurolophus skull last year.

But Robert Sullivan, the senior curator at the State Museum of Pennsylvania who found the 75-million-year-old duck-billed skull, said it suggests a warmer creature.

“My theory is that this dinosaur may have been warmblooded, and may have been using this crest like an elephant uses its ears, to cool itself off,” he said.

Sullivan found the nearly intact fossil skull near Farmington, about 180 miles northwest of Albuquerque.

The crest rises four feet from the back of the dinosaur’s skull, a huge, curved, hollow tusk sweeping up and behind the creature. Its purpose remains a subject of debate. Some researchers say it was a horn for communicating.

Sullivan recently offered a different explanation to the Society of Vertebrate Paleontology. He said it may have acted as a radiator, cooling down--or warming up--the dinosaur.

“We definitely have proof that the Parasaurolophus had a highly vascularized upper crest,” he said. “We suspect that it played some role in thermal regulation.”

As evidence, Sullivan pointed to an intricate web of nasal passages, looping back and down in the crest. Researchers got a peek at the tubing in December, when they ran the fossil through a CT scan machine donated for use at Albuquerque’s St. Joseph Medical Center.

John Ruben, a zoology professor at Oregon State University, recently published research in Science magazine discrediting 20-year-old theories that dinosaurs were warmblooded.

He said the passages in the Parasaurolophus crest are too narrow to allow enough air through them to affect a dinosaur’s blood temperature.

“Pinch your nose with your thumbs until your nostrils are narrow and then try to breathe. You see the problem?” he said. “I go with the theory that this crest is about making noise.”

Jack Horner, curator of paleontology at the Museum of the Rockies in Bozeman, Mont., and coauthor of the Science article, agreed.

“I think it’s some kind of resonating chamber for communicating. That’s it,” he said.

Sullivan and Williamson, however, are not disregarding the horn idea. Working with Sandia National Laboratories computer scientist Carl Diegert, they are building a computerized simulation of the dinosaur’s skull that they will use to recreate the sound the ancient creature might have made.

They also plan to travel to Sweden and Canada to study two other Parasaurolophus fossils.

Patrick Johnson, 11, a budding paleontologist who hangs out at the New Mexico Museum of Natural History, said he has his own theory about the crest.

“I think it’s for digging plants out of the ground, and maybe for scaring away other dinosaurs,” he said. “They probably would brandish that crest and chase them away.”

Sullivan admits they’re all a bit stymied by the whole thing.

“You could argue both sides of this issue with the same evidence,” he said. “Who really knows?”