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T-rex site in Utah suggests giant dinosaurs were social creatures

Southern Utah

“Hollywood” specimen, same species as Teratophoneus, discovered approximately two miles north of the “Rainbows and Unicorns Quarry” on Grand Staircase-Escalante National Monument. (courtesy of Dr. Alan Titus, BLM)

KANAB, Utah (ABC4) – It’s said that teamwork makes the dream work, and based on new discoveries, researchers now believe that the Tyrannosaurus rex bought into that philosophy millions of years ago.

Based on findings made at the Grand Staircase-Escalante National Monument about the fearsome carnivores, the Bureau of Land Management has published new research suggesting that the dinosaur species may have been more social than historically believed. The findings are based on a 2014 discovery of fossils from four or five different T-rexes at the same site inside the monument’s “Rainbows and Unicorns Quarry.”

“Localities [like Rainbows and Unicorns Quarry] that produce insights into the possible behavior of extinct animals are especially rare, and difficult to interpret,” said tyrannosaur expert Dr. Philip Currie in a press release from the Bureau. “Traditional excavation techniques, supplemented by the analysis of rare earth elements, stable isotopes, and charcoal concentrations convincingly show a synchronous death event at the Rainbows site of four or five tyrannosaurids. Undoubtedly, this group died together, which adds to a growing body of evidence that tyrannosaurids were capable of interacting as gregarious packs.” 

Dr. Alan Titus poses with a fossil prepared for transport at Rainbows and Unicorns Quarry (Courtesy of Bureau of Land Management)

Using complex chemical science to determine the age of the fossils found at the site, the research team, which included scientists from the University of Arkansas and the Denver Museum of Nature & Science, were able to conclusively determine that a group of four or five Tyrannosaurus rex died together, suggesting that they lived together and likely hunted and worked together.

Historically speaking, the Tyrannosaurus rex was considered by most dinosaur experts to have been a solitary species, based primarily on the animal’s relatively small brain size, according to the fossil record.

How the T-rex lived and interacted with its environment has long been debated in the paleontology community. Currie first introduced the idea that the giant killers made famous by the Jurassic Park movies could hunt in groups over 20 years ago. This was based on the unearthing of a mass grave of T-rexes in Alberta, Canada. Some skeptics dismissed Currie’s theory, saying that site was not indictive of normal animal behavior. However, the Utah discovery, and an earlier dig in Montana have made Currie’s theory even more compelling, according to the Bureau’s press release.

“The new Utah site adds to the growing body of evidence showing that tyrannosaurs were complex, large predators capable of social behaviors common in many of their living relatives, the birds,” said Dr. Joe Sertich, dinosaur curator at the Denver Museum of Nature & Science who also worked on his project. “This discovery should be the tipping point for reconsidering how these top carnivores behaved and hunted across the northern hemisphere during the Cretaceous.” 

Rainbow and Unicorn Quarry

While it may seem like a fantasy that a dinosaur dig site was named “Rainbow and Unicorn Quarry,” the fossils are the real deal. The name of the site was coined based on a humorous exchange between the researchers.

According to Bureau of Land Management paleontologist Dr. Alan Titus, one of his former employees joked to another that Titus was so excited about what they had found at the site, that it was all “rainbow and unicorns” at the location. The name stuck. Later, as the dig progressed, the scientists brought a plush unicorn mascot, Bruno, to supervise the excavation.

Bruno, the unicorn, watches over the dig at Rainbow and Unicorn Quarry. (Courtesy of Utah Bureau of Land Management)

The quarry has also produced many other fascinating finds, including a seven species of turtle, two other dinosaurs, multiple fish, and a nearly complete 12-foot-long Deinosuchus alligator. These fossils are not believed to have died in a group like the T-rexes, however.

The Bureau plans to continue to conduct trace element and isotopic analysis of the tyrannosaur bones with hopes to further understand the dinosaur’s social behavior.

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