Social T. rex? New research shows that carnivore is hunted in packs

Researchers discovered a pile of dinosaurs at the Grand Staircase-Escalante National Monument – a family of the giant Tyrannosaurus rex – leading them to conclude that they all died at the same time during the same flood and hung out together in a “ cozy ” social unit.

The Rainbows & Unicorns Quarry in southern Utah is groundbreaking because the mainstream story of these dinosaurs that roamed the Earth 76.4 million years ago is that they were solitary prey that lacked the sophistication to launch a coordinated attack. to feed their next meal.

“That takes a lot of brain power,” said Alan Titus, paleontologist at the Bureau of Land Management in Paria River District.

Titus said the finding is “somewhat controversial” because the 2014 find illustrates that the giant dinosaurs traveled together and likely collaborated in killings – like lion pride or wolf packs do today. Paleontological researchers were mostly dismissive of the idea that the giant carnivorous dinosaurs were capable of such social action.

In this find, scientists unearthed a family of four, possibly five individuals of the T. rex, including a young juvenile about 4 years old and a fully developed adult in their mid-twenties.

The site was peeled off using a series of scientific techniques that reveal it to be the first tyrannosaurus mass death site found in the southern United States. Using a series of tests and analyzes of the remains of the original site, researchers found that the dinosaurs perished in a single flood, were buried in fine mud, dug up, and reburied in a sandbar.

“And there it is, a very sad day in southern Utah 76 million years ago,” said Titus.

Alan Titus, Bureau of Land Management

The findings are published by publication in the open access scientific journal PeerJ on Monday. They were created by a team of researchers from the BLM, Denver Museum of Nature and Science, University of Arkansas, Colby College of Maine, and James Cook University in Australia.

The specimens excavated from the unique fossil bone site exceeded expectations, even by the lofty nickname.

Titus said the name derives from teasing former colleagues who blame him for his continued excitement at each new find.

“It’s always about rainbows and unicorns for me,” he said, but stressed that he told his colleagues that this was really a find of rainbows and unicorns.

Researchers remain excited that the quarry will provide more answers the more they dig into it.

“The new Utah site adds to the growing body of evidence showing that tyrannosaurs were complex, large predators capable of social behaviors that many of their living relatives, the birds, have,” said project officer Joe Sertich, curator. dinosaurs at the Denver Museum of Nature and Science. “This discovery should be the tipping point to rethink how these top carnivores behaved and hunted across the Northern Hemisphere during the Cretaceous Period.”

Titus explained that the large predators don’t usually cooperate in the search for food – after all, they compete against each other.

But as in the case of lions and wolves, which have complex and sophisticated social roles, Titus said that a modern-day dinosaur great-nephew – Harris’s hawk – is the only known bird of prey to hunt together and participate in the communal upbringing of their young. . .

Alan Titus, Bureau of Land Management

“Places (such as Rainbows and Unicorns Quarry) that provide insight into the possible behavior of extinct animals are extremely rare and difficult to interpret,” said world-renowned tyrannosaur expert Philip Currie. “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. This group undoubtedly died together, adding to a growing body of evidence that tyrannosaurids were able to work together as sociable packs. ”

The idea that tyrannosaurs were social with complex hunting strategies was first formulated by Currie more than 20 years ago.

Alan Titus, Bureau of Land Management