The Tyrannosaurus rex may not have been as lonely as we thought.
In a groundbreaking discovery of the first T. rex mass death site in the southern United States, announced Monday by the Utah Bureau of Land Management, scientists found evidence of pack behavior among the famous ancient predator in the Grand Staircase-Escalante National Monument.
“The new Utah site adds to the growing body of evidence showing that tyrannosaurs were large, complex predators capable of social behaviors common to many of their living relatives, the birds,” said Dr. Joe Sertich, curator of dinosaurs at the Denver Museum of Nature and Science.
“This finding should be the tipping point to reconsider how these large carnivores behaved and hunted in the northern hemisphere during the Cretaceous.”
In the past, paleontologists have long debated whether huge dinosaurs lived and hunted alone or in groups.
However, along with other findings of pack formations in Alberta, Canada, and Montana, the Utah find may fossilize the belief of a social T. rex.
In the Canadian discovery, 12 individuals found over 20 years ago by Dr Philip Currie, many scientists doubted T. rexes had the brain to organize itself into something complex and thought it was ‘an isolated case. The Montana site was based on social theory, but now this third site can bring more certainty to the idea.
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At the site of the rainbows and unicorns in the monument’s Kaiparowits unit, named after the incredible finds that have been unearthed there, scientists have been working on the social conclusion of dinosaurs since 2014.
“We immediately realized that this site could potentially be used to test the idea of the social tyrannosaurus. Unfortunately, the ancient history of the site is complicated, ”said Dr. Alan Titus, BLM paleontologist.
A group of four, perhaps five, Teratophoneus T. rexes appeared to have died from seasonal flooding after a slow-burning fire 66-100 million years ago. Turtles, fish, rays, alligators and two other types of dinosaurs were also found during excavations.
Their bones were later exhumed by a flowing river and re-buried, making the discovery more puzzling.
The research of Dr. Celina Suarez, associate professor of geology at the University of Arkansas, and her former doctorate. The student, Dr. Daigo Yamamura, has definitely shown that dinosaurs move in packs.
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“None of the physical evidence conclusively suggested that these organisms fossilized together, so we turned to geochemistry to see if that could help us. The similarity of the rare earth element patterns strongly suggests that these organisms are dead and fossilized together, ”Suarez says.
The excavation will continue “for the foreseeable future,” according to a press release, and will include more research into the behavior of T. rex.
Follow K. Sophie Will on Twitter at @ksophiewill.