New Species of Allosaurus Discovered in Rocks of Utah

(CN) – Scientists have discovered a new species of allosaurus in northeast Utah – only the second of its kind known to have roamed what is now North America in the Jurassic period.

In a study published Friday in the scientific journal PeerJ, a team of paleontologists revealed they have identified a new species of allosauroid, a carnivorous class of two-legged dinosaurs well known for being leading predators in the Jurassic and Cretaceous periods, at the Dinosaur National Monument in Utah. While the initial skeleton of the new species – named Allosaurus jimmadseni in honor of the late Utah State paleontologist James Madsen Jr. who significantly contributed to the general understanding of the allosaurus – was discovered 30 years ago, it has never been identified as being a completely new variety of allosauroid before this announcement.

Illustration of allosaurus jimmadseni attacking juvenile sauropod. (Todd Marshall)

The study notes that the Allosaurus jimmadseni had numerous notable features that would have allowed it to stand out during its time on Earth. Not only did it weigh around 4,000 pounds and stretch nearly 30 feet long, it also had a uniquely thin and narrow skull with horns in front of its eye and 80 teeth in its mouth. It had surprisingly long legs and clawed arms.

One of the most significant revelations of this discovery, however, is that before this study, it was largely believed that only one other type of Allosaurus occupied North America during the Jurassic period, the Allosaurus fragilis.

Mark Loewen, co-author 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, says that the importance of the discovery is also in the fact that the Allosaurus jimmadseni evolved much earlier than the previously known Allosaurus fragilis species.

“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,” Loewen said with the release of the study.

Allosaurus jimmadseni. (Ashley Atuchin)

Researchers say the Allosaurus jimmadseni likely lived on and around the western floodplains of North America, a habitat well suited to their predatory and carnivorous lifestyle. Dating of the fossils suggest that the creature lived around 152-157 million years ago, making it the oldest species of allosaurus known today.

One aspect of allosaurus history that is well debated among scientific circles is just how many types of known dinosaurs belong to the allosaurus family. Paleontologists have debates for over a century on how many dinosaur species lived in western North America, with some believing only one and some saying up to a dozen. Data and fossil examination in this study suggest, however, there were in fact two.

Daniel Chure, another co-lead author of the study and retired paleontologist at Dinosaur National Monument, says this discovery serves as reminder that the ancient history of dinosaurs is one littered with many mysteries still to be unraveled, and there are many more discoveries to be made going forward.

“Recognizing a new species of dinosaur in rocks that have been intensely investigated for over 150 years is an outstanding experience of discovery. 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 said with the release of the study.

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