A remarkable fossil site in Utah, where several tyrannosaurs were found buried together, bolsters a nascent theory that these terrifying creatures hunted in packs, similar to wolves.
That tyrannosaurs were social hunters has been a possibility paleontologists have considered for over 20 years. In 1910, paleontologists working in Alberta, Canada discovered the remains of 12 tyrannosaurs that appeared to have died together. This discovery was largely forgotten until Canadian paleontologist Philip Currie, now affiliated with the University of Alberta, revisited the old find in 1998. fight that was evidence of “gregarious behavior” in tyrannosaurs and that these animals were pack hunters.
Seven years later, Currie, along with a number of colleagues, reported at a similar discovery made in Montana, showing the remains of three tyrannosaurs, belonging to the genus Daspletosaurus, were also found together. And in 2014 paleontologists described fossilized dino footprints found in British Columbia, Canada, which appeared to show three tyrannosaurs moving in the same direction at the same time.
Despite this evidence, scientists were reluctant to attribute tyrannosaurs to companionship, arguing that dinosaurs’ limited cognitive abilities could not have allowed it. Critics of this theory will now have to consider a third mass death site, as outlined in a new one paper published in PeerJ.
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The fossil site is in the Grand Staircase-Escalante National Monument, and it yielded the remains of four, possibly five tyrannosaurs, all of which appeared to have died at the same time. The fossils were buried at the site of a former river, and the authors of the new paper said their deaths were likely the result of seasonal flooding.
“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,” Joe Sertich, a co-. author of the paper and curator of dinosaurs at the Denver Museum of Nature & Science, explained in a press release. “This discovery should be the tipping point to rethink how these top carnivores behaved and hunted across the Northern Hemisphere during the Cretaceous Period.”
Currie, who was not involved in the new study, said the finding “adds to a growing body of evidence that tyrannosaurides were able to work together as group groups,” as he was quoted in the press release prepared by Utah’s Bureau of Land Management.
The bones of these dinosaurs were found buried in the late Campania-era Kaiparowits Formation in southern Utah, which bears the beautiful nickname “Rainbows and Unicorns Quarry”. Study co-author Alan Titus of the Bureau of Land Management discovered the site in 2014, and it represents the first tyrannosaurus mass death site in the southern United States.
Titus and his colleagues discovered the remains of several Teratophoneus, a genus of tyrannosaurs that lived in the Cretaceous period about 77 million up to 76 million years ago. This genus is known under a single species, Teratophoneus curriei, whose largest members are anywhere from 21 to 26 feet (6.4 yrs 7.9 meters) long. Tyrannosaurs, or tyrannosaurids, describe a family of oversized carnivorous dinosaurs standing on two legs, the best known examples of which are: Tyrannosaurus rex, Albertosaurus, Daspletosaurus, and Tarbosaurus.
In addition to the Teratophoneus fossils, Titus and his colleagues discovered several turtles, different species of fish and rays, an almost complete skeleton of a 3 meter long (3.7-meters) Deinosuchus alligator, and two other dinosaur species (none of these animals are believed to have died in the event that the Teratophoneus copies). In addition to these bones, the scientists collected fragments of small rocks and sandbar deposits from the former Cretaceous river.
“We immediately realized that this site could potentially be used to test the idea of social tyrannosaurs. Unfortunately, the site’s ancient history is complicated, ”said Titus. “With bones that appear to have been dug up and reburied by the action of a river, the original context in which they lay has been destroyed. But all is not lost. ”
Indeed, both chemical and physical evidence recovered from the site allowed the team to understand this ancient scene, despite the geological perturbations mentioned above. Analysis of stable carbon and oxygen isotopes, along with rare earth element concentrations, yielded “a relatively homogeneous signature,” as the paleontologists wrote in their paper. This strongly suggests that the fossils were all from the same source population and that the animals died and were petrified together. It also suggests that no other animals were introduced to the cemetery at a later date.
The scientists suspect a seasonal flood killed the tyrannosaurs and washed their bodies in a nearby lake, where they were eventually buried. The team offered several other options to explain the mass deaths, including poisoning (eg drinking water contaminated with cyanobacteria), drought, fire and even drowning in quicksand. Flooding is considered the most plausible explanation of these scenarios, according to the scientists.
The find in the Rainbows and Unicorns Quarry is clearly a big deal as it is potential evidence for not just cooperative hunting among tyrannosaurs but sociality in general, which could also apply to other domains, namely comprehensive parental care. That said, not everyone is convinced by the new evidence.
“It’s a bit harder to be so sure that these data mean that these tyrannosaurs lived together in good times,” said Kristi Curry Rogers, a professor of biology at Macalester College. Associated Press. “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.”
Fair enough. Just because these dino bodies were all buried together doesn’t automatically mean they actually took part in the parcel hunt. As Rogers suggests, the Teratophoneus Dinosaurs may have gathered to feast on a fallen animal, which may or may not have been typical behavior for these theropods. For example, vultures amount to a communal meal, but these birds can hardly be described as pack hunters.
Consequently, other evidence will be needed to support this hypothesis, notably evidence to show that these animals willingly hung out with each other. and that they did so in a cooperative way. That won’t be easy to prove, but no one said paleontology was easy.
More: Dinosaurs love T. rex were more tyrannical than we realized, research suggests.