Imagine being chased by a Tyrannosaurus rex. Now imagine being chased by six. That might've been the scenario for T. rex prey, according to new research suggesting the dino predator hunted in packs like wolves. The theory stems from a site discovered in 2014 at the Grand Staircase-Escalante National Monument in southern Utah. Dubbed the "Rainbows and Unicorns quarry because of the vast array of fossils contained inside," per the Guardian, the site includes the remains of four or five T. rex who lived and died in the same place during a seasonal flood between 66 million and 100 million years ago. "The similarity of rare earth element patterns is highly suggestive that these organisms died and were fossilized together," meaning they were moving in a pack, Celina Suarez of the University of Arkansas, co-author of the study published Monday in PeerJ, tells the St. George Spectrum & Daily News.
Researchers located fossils of other animals thought to have succumbed to the flood, but it doesn't seem like they'd died together. Some argue the tyrannosaurs were forced together due to a lack of resources. But this is the third mass T. rex death site found in North America, after others in Montana and Alberta. Alan Titus, the paleontologist who discovered the Utah site, says there's debate about whether T. rex had a brain capable of sophisticated social interaction. But "this discovery should be the tipping point for reconsidering how these top carnivores behaved and hunted," Joe Sertich, curator of dinosaurs at the Denver Museum of Nature & Science, tells the Spectrum. He notes tyrannosaurs were likely "capable of social behaviors common in many of their living relatives, the birds." The study follows another that suggests 20,000 T. rex roamed the continent at one time, per National Geographic. (More on that research here.)