There’s a new dinosaur at the Utah Museum of Natural History, and its name is Allosaurus jimmadseni.

Well, it’s not exactly new. According to scientists, the carnivorous beast roamed western North America between 157-152 million years ago, during the Late Jurassic Period. And it was formidable — 26-29 feet long and weighing in at about 4,000 pounds. It was the top predator in its ecosystem, with relatively long legs and tail, and long arms with three sharp claws.

The first specimen was excavated in Dinosaur National Monument in northeastern Utah from 1990-94; the skull was found in 1996.

“Recognizing a new species of dinosaur in rocks that have been intensely investigated for over 150 years is an outstanding experience of discovery,” said Daniel Chure, retired paleontologist at Dinosaur National Monument and co-lead author of the study published in PeerJ Life & Environment. “Allosaurus jimmadseni is a great example of just how much more we have to learn about the world of dinosaurs.”

The study was funded in part by the University of Utah, the National Park Service and the National Science Found.

(Photo courtesy of the J. Willard Marriott Library) Paleontologist James Madsen Jr. assembles a composite skeleton of Allosaurus.

The dinosaur was named in honor of former state paleontologist James Madsen Jr., who excavated and studied tens of thousands of Allosaurus bones from the Cleveland-Lloyd Dinosaur Quarry in central Utah. He died in 2009 at the age of 77.

And the “new” Allosaurus is actually millions of years older than Utah’s state fossil, Allosaurus fragilis.

Paleontologists had believed there was just one species of Allosaurus in Jurassic North America, according to Mark Loewen, one of the lead authors of the study and a research associate at the Natural History Museum of Utah and associate professor in the Department of Geology and Geophysics at the University of Utah. “But this study shows there were two species — the newly described Allosaurus jimmadseni evolved at least 5 million years earlier than its younger cousin, Allosaurus fragilis,” he said.

It took seven years to prepare the skeleton of Allosaurus jimmadseni that’s now on display at the Utah Museum of Natural History; much of the work was done by Dinosaur National Monument employees Scott Madsen and Ann Elder, with assistance from volunteers and students at Brigham Young University.