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Alaska's Perot dinosaur had 'wrong-way' horns, study says

Yereth Rosen
What made Alaska's pachyrhinosaurus dinosaur, found on the North Slope, different than other species? It appears that horns, frills and brawn -- not brain power -- set it apart from the rest. Illustration by Karen Carr

Why is Alaska’s pachyrhinosaurus species different from all other pachyrhinosaurus species? Apparently, it comes down to what was on the outside of the skull, not the brainpower that was inside.

A new study by Tony Fiorillo and Ronald Tykoski, discoverers of a previously unknown species of pachyrhinosaurus that lived on Alaska's North Slope during the Cretaceous period, concludes that there was nothing special about its brain size.

The Pachyrhinosaurus perotorum -- the species of horned, plant-eating dinosaur unearthed in 2006 from a bluff along the Colville River -- had a braincase nearly identical to that of other pachyrhinosaurus species, the study says. What distinguishes the Alaska dinosaur is the pattern of horns and frills on the skull, said Fioillo, curator of earth sciences of the Perot Museum of Nature and Science in Dallas.

Scientists have been pondering the question of how to differentiate among the species of armored herbivore dinosaur known as pachyrhinosaurus, Fiorillo said. The latest information about the Alaska dinosaur gets scientists closer to an answer.

"Really, the frill differences are what make or break a different pachyrhinosaurus species," Fiorillo said in a telephone interview.

It took years after the bones were found to analyze them and conclude that they were the remains of a previously unknown species. In 2011, it was named Pachyrhinosaurus perotorum, in honor of Texas billionaire and one-time presidential candidate Ross Perot and his family, patrons of Fiorillo’s museum.

Earlier this year, Fiorillo and Tykoski, the museum’s fossil preparer, announced that they had found, among the bones of the adult, a juvenile member of the species.

The Perot dinosaur has very distinctive frill patterns, with an extra dome that doesn’t appear on other pachyrhinosarus species, among other features. There are spikes and horns that differ from other species, including "a horn going the wrong way."

Though the Perot dinosaur did not seem particularly brainy -- the brain was relatively small compared to its body mass -- it was savvy enough to cope with Cretaceous-era Alaska, Fiorillo said.

"They were certainly smart enough to have lasted millions of years," he said.

The original skull pulled from the Colville River bluff and a model of the Perot dinosaur’s skeleton are now on display at the museum in Dallas, Fiorillo said.

Alaska dinosaur discoveries are significant because they prove the prehistoric animals could survive in cold, dark climates. The land that is now Alaska was not as cold in the Cretaceous as it is presently, but it was not tropical, either. The climate was more like that of the Pacific Northwest or northern Rocky Mountains. Winters were also darker -- today’s Alaska was, at that time, much farther north.

Discoveries about Arctic dinosaurs support the contention that the prehistoric animals -- or some of them -- were at least partially warm-blooded. That theory is examined in a NOVA documentary that filmed at the Colville River when Fiorillo’s team unearthed the Perot dinosaur’s skull.

Contact Yereth Rosen at yereth(at)alaskadispatch.com