Tyrannosaurus dinosaurs may not have been solitary predators for long, but more like social carnivores like wolves, new research announced Monday has found.
Paleontologists developed the theory while studying a massive tyrannosaurus death site found seven years ago in the Grand Staircase-Escalante National Monument in southern Utah, one of two monuments the Biden government is considering restoring to full size after former President Donald Trump had shrunk them.
Using geochemical analysis of the bones and rock, a team of researchers at the University of Arkansas determined that the dinosaurs died and were buried in the same place and were not the result of fossils coming from multiple areas.
Kristi Curry Rogers, a biology professor at Macalester College, said this research is a “ good start, ” but more evidence is needed before determining that the tyrannosaurs lived in a social group.
“It’s a bit more difficult to be so sure that these data mean that these tyrannosaurs lived together in good times,” Rogers said. “It’s possible that these animals lived in the same neighborhood as each other without traveling together in a social group, and just congregated around dwindling resources as times got tougher.”
In 2014, paleontologist Alan Titus of Bureau of Land Management discovered the site, which was later named the Rainbows and Unicorns quarry due to the sheer amount of fossils it contains. Excavations have been ongoing since the discovery of the site due to the size of the area and the volume of bones.
“I consider this a once-in-a-lifetime discovery for myself,” Titus told reporters during a virtual press conference. “I probably won’t find another site in my career that is so exciting and scientifically significant.”
The new Utah site is the third massive tyrannosaur burial site discovered in North America and provides further evidence that tyrannosaurs may have lived in groups, Titus said.
The theory of social tyrannosaurs began more than 20 years ago when more than a dozen tyrannosaurs were found at a site in Alberta, Canada. Another mass death site in Montana once again raised the possibility of social tyrannosaurs. Many scientists questioned the theory, arguing that the dinosaurs did not have the brain power to engage in advanced social interaction, Titus said.
“Taking that next step to understand behavior and how animals behave really takes astonishing evidence,” Joseph Sertich, dinosaur curator at the Denver Museum of Nature & Science, said at the press conference. “I think this site, the spectacular collection of tyrannosaurs but also the other evidence collected … is pushing us so far as to show some evidence of behavior.”
In addition to the tyrannosaurs, researchers have also found seven species of turtles, multiple species of fish and rays, two other types of dinosaurs, and an almost complete skeleton of a juvenile Deinosuchus alligator. These other animals don’t all seem to have died together.
Paleontology groups were among those pushing the federal government to restore the Bears Ears National Monument and Grand Staircase-Escalante to their original size to protect the region’s rich paleontological and archaeological record.
Home Secretary Deb Haaland visited southern Utah earlier this month as she prepared to make recommendations on whether or not to reverse Trump’s decision to shrink the monuments. Titus said he showed Haaland some of the fossils in his lab during her visit and said she “appreciated seeing the material.”
“The (Bureau of Land Management) protects these fossils as national treasures,” Titus said. “They are part of the story of how North America came to be and how we eventually came to be.”