As the most vicious dinosaur, Tyrannosaurus rex once roamed with impunity the lands that now make up North America. And if the conclusions of a new research project are correct, their behavior may have been even more frightening and intimidating than previously thought. According to an article published in the open access journal on April 19 PeerJ: Life and environment , Tyrannosaurus rex was most likely not a lone hunter, but rather worked in packs to chase, surround, and greedily devour the animals on which they depended for food, such as wolves.
A circular display of Tyrannosaurus rex skulls. ( Kumiko of Tokyo, Japan / CC BY-SA 2.0 )
Tyrannosaurus Rex: The complex truth finally emerges
This fascinating and somewhat disturbing discovery emerges from a study conducted by a team of paleontologists working with the U.S. Bureau of Land Management (BLM) in Utah.
The scientists conducted an extensive analysis of a diverse collection of Tyrannosaurus rex bones found at a Cretaceous fossil site in southern Utah, located near the Grand Staircase-Escalante National Monument. This site is popularly known as the “Rainbows and Unicorns Quarry”, in recognition of all the rare fossils (the “unicorns”) that have been excavated there.
Paleontologist Alan Titus, who discovered the website Rainbows and Unicorns in 2014 and is one of the lead authors of the PeerJ study, says that the group of dead and petrified Tyrannosaurus rex monsters were the victims of a massive flood that drowned them and washed their bodies in a lake. They grouped for millions of years and lay undisturbed on the ground until climatological and geological changes dried up the lake and created a river (also now gone) that eroded the soil and brought the bones back to the earth’s surface.
“We used a true multidisciplinary approach (physical and chemical evidence) to put together the history of the site,” explained Celina Suarez, a geologist and participant in the study. ‘The end result [was] that the tyrannosaurs died together during a seasonal flood event. ”
The members of the BLM research team consider their findings to be indirect but clear evidence of group dynamics in action among the Tyrannosaurus rex samples involved. Their collaborative behavior would have been survival-oriented, focused on group hunting and possibly also enabled extensive parental care, the scientists say.
“The new Utah website contributes to the growing body of evidence showing that tyrannosaurs were complex, large predators that were able to have social behaviors common to many of their living relatives, the birds,” said Joe Sertich, researcher at the research project, which is the dinosaur curator at Museum of Nature and Science in Denver. “This discovery should be the turning point in reconsidering how these top carnivores behaved and hunted across the northern hemisphere during the Cretaceous.”
A family of Tyrannosaurus rex dinosaurs on the run. ( Orlando Florin Rosu / Adobe Stock)
Slowly and steadily win the race
Earlier evidence in support of the thesis that Tyrannosaurus rex was hunted in packs appeared in 2020 when Canadian scientists published the results of their study on the physiology and anatomy of tyrannosaurus in the May issue of the journal. PLOS Een .
Contrary to previous claims, which claimed that Tyrannosaurus rex could travel at a speed of up to 70 kilometers per hour, the Canadian researchers concluded that a T. rex in a sprint would not be able to to reach the 12 miles per hour. hour (20 kilometers per hour) mark. However, the T. rex anatomy would have enabled them to continue at that speed for considerable distances, according to Professor McGill University, Hans Larsson.
‘If it were their way of hunting, it could go much greater distances at a reasonable distance [but not great] clip, what kind of lifestyle would that be? “The animals that do this today are animals, like wolves, that hunt in packs,” Larsson said.
It also mentions that the bone bed in southern Utah is not the first mass Tyrannosaurus rex tomb discovered on the North American continent. Two decades ago, more than a dozen different T. rex fossils were found buried together at a site in Red Deer, Alberta, Canada, and another large T. rex burial was unearthed in Montana a few years later.
If the package hypothesis is true, no doubt such discoveries await.
Tyrannosaurus rex attacking an Einiosaurus. ( Elenarts / Adobe Stock)
Imagine your countless packs of hunger T. Rexes on the hunt
If Tyrannosaurus rex hunted in teams, as the growing body of evidence suggests, their group togetherness would have given them evolutionary advantages that would be reflected in their population numbers.
During their 2.5 million year reign as king of the dinosaurs, the mighty Tyrannosaurus rex was always the predator and never the prey. Consequently, population growth would be poorly controlled, except for the occasional food shortage (which was probably scarce on a prehistoric earth teeming with animal life).
Which begs an interesting question: exactly how many Tyrannosaurus rex specimens lived and died on the North American continent before the entire species became extinct about 65 million years ago?
A team of scientists and science students from the University of California-Berkeley have been trying to find the answer to this interesting question. They collected all the data on Tyrannosaurus rex obtained from the fossil record and used the information to calculate the average T. rex lifespan, along with the animal’s nutritional needs and probable breeding skills.
After knocking down all the numbers, the Cal-Berkeley team determined that there would be approximately 20,000 individual animals living on the 1.4 million square kilometers (2.3 million square kilometers) of available habitat space at one time. They estimated that every 19 years a new generation would be born, and that about 127,000 generations of T. rex would have existed during the 2.5 million years of species’ lifespan.
If these estimates are correct, and scientists claim that it is 95 percent certain that it is, then it means that 2.5 billion Tyrannosaurus rexes lived and died on this planet. If they had traveled in groups of 10 to 20, between one and two thousand T. rex packs would have wandered around the continent at any given time in search of food.
Assuming this was the case, the animals on which T. rex slaughtered would have enjoyed precious few moments of tranquility. Once one thundering herd of the most terrifying predator the planet has ever produced has passed, another would soon arrive from beyond the horizon, and the new herd would be just as ferocious as the one that preceded it.
If humans ever perfected the science of time travel, we should probably think twice about visiting the North American continent during the Late Cretaceous.
Top image: According to the latest scientific study, tyrannosaurus rex is hunted in packs, just like wolves. Source: warpaintcobra / Adobe Stock
By Nathan Falde