Jurassic Giant Discovered

A remarkable new species of meat-eating dinosaur has been unveiled at the Natural History Museum of Utah. Paleontologists unearthed the first specimen in the early 1990s in Dinosaur National Monument in northeastern Utah. The huge carnivore inhabited the flood plains of western North America during the Late Jurassic Period, between 157 and 152 million years ago, making it the geologically oldest species of Allosaurus, predating the more well-known state fossil of Utah, Allosaurus fragilis. The new dinosaur, Allosaurus jimmadseni, was named after Utah’s first state paleontologist, James H. Madsen, Jr. MS’57, who excavated thousands of Allosaurus bones from a dinosaur quarry in central Utah and published a book about his findings in 1976.

Weighing approximately 4,000 pounds and measuring up to 29 feet long, with 80 sharp teeth, this Allosaurus was the top predator in its ecosystem. Before its discovery, paleontologists thought only one species of Allosaurus existed, but this newly discovered dinosaur evolved at least 5 million years earlier than its younger cousin. Allosaurus jimmadseni has a narrower back of the skull, and a weaker and lighter skull, suggesting a different diet.

The two scientists behind the discovery, Dan Chure and Mark Loewen PhD’09, have studied nearly every Allosaurus bone in existence, says Chure. The first skeleton of the new dino was excavated from 1990 to 1994, and the skull wasn’t found until 1996. It took explosives to remove surrounding rock and a helicopter to fly the 2,700-kilogram block to the museum for analysis. Discovering that the specimen was an entirely new species was an extensive process. Just fully preparing all the bones for examination took seven years.

“Allosaurus jimmadseni is a great example of just how much more we have to learn about the world of dinosaurs. Many more exciting fossils await discovery in the Jurassic rocks of the American West,” Chure says.

Other fossils previously thought to have belonged to Allosaurus fragilis have now been identified as the newly discovered species. And fossils are housed at museums in Montana, South Dakota, Switzerland, Brigham Young University, and of course the U’s own Natural History Museum of Utah, which boasts the world’s largest collection of Allosaurus fossils.