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Credit: Andrey Atuchin

Utah paleontologists unveil new species of fearsome apex predator, Allosaurus

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Jan 27, 2020

A previously unknown species of carnivorous dinosaur has just been revealed to the public inside the echoing halls at the Natural History Museum of Utah. Paleontologists are thrilled to have now identified this older dino relative of the fearsome Allosaurus fragilis (the official state fossil) that once roamed the arid flood plains of what's now known as the Morrison Formation in the western United States.

This second species was officially named Allosaurus jimmadseni in a new study revealed last week in the online scientific journal PeerJ. Researchers detailed how George Engelmann of the University of Nebraska first unearthed the Late Jurassic creature's headless skeletal remains back in 1990 from northeastern Utah's Dinosaur National Monument. It was discovered encased in a 6,000-pound block of rock and required explosives to free it from its impenetrable tomb.

Credit: Todd Marshall - Allosaurus jimmadseni attack juvenile sauropod

Six years later, the beast's head was found in the same area by retired radiologist Ramal Jones and his handy radiation detector. The massive skull, containing radioactive elements absorbed by the surrounding soil, was located close to where its body was uncovered. A team from Dinosaur National Monument later excavated the dinosaur head and reunited it with the rest of its skeleton, which allowed paleontologist to recognize the specimen as a newly-discovered species.

Credit: Daniel J. Chure, Mark A. Loewen

"Previously, paleontologists thought there was only one species of Allosaurus in Jurassic North America, 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," said study co-author Mark Loewen, associate professor in the Department of Geology and Geophysics at the University of Utah. "The skull of Allosaurus jimmadseni is more lightly built than its later relative Allosaurus fragilis, suggesting a different feeding behavior between the two."

This meat-eating dinosaur was an imposing apex predator, measuring up to 29 feet long and tipping the scales at approximately 4,000 lbs. It sported a more narrowed skull packed with 80 deadly teeth, two horns in front of its eyes, and a long crest that extended down from horns to snout. Its long arms were equipped with three razor-sharp claws to expertly snare and slash prey. 

Credit: Daniel J. Chure, Mark A. Loewen

The intimidating beast's freshly catalogued title recognizes the late Utah State Paleontologist James H. Madsen Jr., in honor of his "herculean efforts of protecting, excavating, preparing and curating of many thousands of Allosaurus bones," collected from Utah's Cleveland-Lloyd Dinosaur Quarry.

"Recognizing a new species of dinosaur in rocks that have been intensely investigated for over 150 years is an outstanding experience of discovery," said study co-author Daniel Chure, retired paleontologist at Dinosaur National Monument. "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."


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