A remarkable Utah fossil site, in which several tyrannosaurs were found buried together, reinforces an emerging theory that these terrifying creatures are hunted in packs, similar to wolves.
That tyrannosaurs are social hunters is a possibility paleontologists have been considering for more than 20 years. In 1910, paleontologists discovering in Alberta, Canada, the remains of 12 tyrannosaurs who had apparently died. together. This discovery was largely forgotten until Canadian paleontologist Philip Currie, now working with the University of Alberta, revisited the old finding in 1998, argue that it was evidence of “active behavior” in tyrannosaurs and that these animals were pack hunters.
Seven years later, Currie, along with several colleagues, report on a similar discovery made in Montana, in which the remains of three tyrannosaurs, belonging to the genus Daspletosaurus, was also found together. And in 2014, paleontologists describe petrified dino footprints found in British Columbia, Canada, and it appears that three tyrannosaurs are moving in the same direction at the same time.
Despite this evidence, scientists have been reluctant to attribute malicious behavior to tyrannosaurs, claiming that the limited cognitive abilities of dinosaurs could make this impossible. Critics of this theory will now have to consider a third mass death, as described in a new article paper published in PeerJ.
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The fossil site is located within the Grand Staircase-Escalante National Monument, and it yielded the remains of four, possibly five, tyrannosaurs, all of which apparently died at the same time. The fossils were buried at the site of a former river, and the authors of the new article said their deaths were likely due to seasonal flooding.
“The new site in Utah contributes to the growing body of evidence showing that tyrannosaurs were complex, large predators that were able to prevent social behavior common to many of their living relatives, the birds,” said Joe Sertich, a co-author of the newspaper and curator of dinosaurs. in the Denver Museum of Nature & Science, explained in a Press release. “This discovery should be the turning point in reconsidering how these top carnivores behaved and hunted across the northern hemisphere during the Cretaceous.”
Currie, who was not involved in the new study, said the finding “contributes to a growing body of evidence that tyrannosaurids are able to work together as fusing packs,” as he was quoted as saying in the press release. by Utah’s Land Management Bureau..
The bones of these dinosaurs were buried in the late-campaign Kaiparowits Formation in southern Utah, nicknamed the ‘Rainbows and Unicorns Quarry’. Study co-author Alan Titus of the Bureau of Land Management discovered the site in 2014, and it is the first tyrannosaurus mass death site found in the southern United States.
Titus and his colleagues uncovered the remains of several Teratophone, a species of tyrannosaurus that inhabited about 77 million in the Cretaceous to 76 million years ago. This species is known by a single species, Teratophoneus currieiof which the largest members are somewhere between 21 and 26 feet (6.4 and 7.9 meters) long. Tyrannosaurs, or tyrannosaurides, describe a family of large carnivorous dinosaurs that stood on two legs, the best known examples of which are Tyrannosaurus rex, Albertosaurus, Daspletosaurus, en Tarbosaurus.
In addition to the Teratophone fossils, Titus and his colleagues discovered several turtles, different species of fish and rays, an almost complete skeleton of a 12-foot-foot (3,7-meter) Deinosuchus crocodile, and two other dinosaur species (it is suspected that none of these animals died in the case of the Teratophone copies). In addition to these bones, scientists have collected fragments of small rocks and sandbank deposits from the former Cretaceous River.
‘We immediately realized that this site could possibly be used to test the social tyrannosaurus idea. “Unfortunately, the ancient history of the site is complicated,” said Titus. ‘It seems that bones were dug up and buried by the action of a river, and the original context in which it lies has been destroyed. However, not everything was lost. ”
Indeed, both chemical and physical evidence found from the site enabled the team to make sense of this ancient scene, despite the above-mentioned geological disruptions. Analysis of stable carbon and oxygen isotopes, coupled with concentrations of rare earth elements, yielded a relatively homogeneous signature, as the paleontologists wrote in their paper. This strongly indicates that the fossils are all from the same source population and that the animals died and became petrified together. It also indicates that no other animals were later brought to the cemetery.
The scientists suspect that tyrannosaurs were killed by a seasonal flood and their bodies were in a lake in the area, where they were eventually buried. The team undertook several other possibilities to explain the mass death, including poisoning (e.g. drinking water contaminated with cyanobacteria), drought, fire and even drowning in quicksand. According to scientists, the flood is considered the most plausible explanation.
The find at the Rainbows and Unicorns Quarry is obviously a big problem, as it is possible evidence for not just collaborative hunting among tyrannosaurs. but sociability in general, which can also apply to other domains, namely extended parental care. That said, not everyone is convinced by the new evidence.
“It’s a little harder to be so sure that these data mean that these tyrannosaurs lived together in the good times,” Kristi Curry Rogers, a biology professor at Macalester College, told the Associated Press. “It is possible that these animals lived in the same environment as each other without traveling together in a social group, and just as the times became more difficult to shrink resources.”
Fair enough. Just because these dino bodies were all buried together does not automatically mean that they participated in pack hunting. As Rogers suggests, the Teratophone dinosaurs may have come together to feast on a fallen animal, which may or may not have been typical behavior for this teropod. Vultures, for example, come to a regular meal, but these birds can hardly be described as hunters.
Consequently, other evidence will be needed to strengthen this hypothesis, specifically evidence to show that these animals willingly socialized with each other. and that they did so in a cooperative manner. It will not be easy to prove, but no one has said paleontology is easy.
More: Dinosaurs like T. rex was more tyrannical than we realized, research suggests.