If there's anything more terrifying than a T rex, it's a pack of T rexes on the prowl, right?
Well, a new study has concluded the infamous carnivores and their cousins weren't solitary hunters as previously believed - they hunted in packs, like wolves.
The remains of five tyrannosaurs of the same species have been uncovered at a site in Utah.
"This supports our hypothesis that these tyrannosaurs died in this site and were all fossilised together; they all died together, and this information is key to our interpretation that the animals were likely gregarious in their behavior," said Celina Suarez, University of Arkansas associate professor of geosciences.
The bones were found at a dig site known as 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 Bureau of Land Management 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."
It's believed they were all killed at the same time in a flood.
"None of the physical evidence conclusively suggested that these organisms came to be fossilized together, so we turned to geochemistry to see if that could help us. The similarity of rare earth element patterns is highly suggestive that these organisms died and were fossilised together," said Prof Suarez.
Previously scientists had doubt tyrannosaurs - which include species like Tyrannosaurus rex, Gorgosaurus and Lythronax, had the intelligence to work in groups.
"This group died together, which adds to a growing body of evidence that tyrannosaurids were capable of interacting as gregarious packs."
The study was published in journal PeerJ this week.