As the fiercest dinosaur, the Tyrannosaurus rex roamed the lands that now form North America with impunity. And if the findings of a new research project are correct, their behavior may have been even more frightening and intimidating than previously imagined. According to an article published April 19 in the open access journal PeerJ: Life and the Environment , Tyrannosaurus rex was probably not a solitary hunter, but worked in packs, to chase, surround, and voraciously consume the animals on which they depended for food, such as wolves.
A circular sample of Tyrannosaurus rex skulls. ( Kumiko of Tokyo, Japan / CC BY-SA 2.0 )
Tyrannosaurus Rex: The complex truth finally emerges
This fascinating and somewhat puzzling discovery emerged from a study conducted by a team of paleontologists working with the U.S. Bureau of Land Management (BLM) office in Utah.
Scientists conducted an extensive analysis of a diverse collection of Tyrannosaurus rex bones found in a fertile Cretaceous fossil site in southern Utah, located near the Grand Staircase-Escalante National Monument. This place is colloquially known as the “Rainbow and Unicorn Quarry”, in recognition of all the rare fossils (the “unicorns”) that have been unearthed.
Paleontologist Alan Titus, who discovered the Rainbows and Unicorns site in 2014 and is one of the lead authors of the PeerJ One study says the group of dead and fossilized rex tyrannosaurs were the victims of a massive flood that drowned them and washed their bodies in a lake. They remained at the bottom, grouped and uncomfortable, for millions of years, until climatic and geological changes dried up the lake and created a river (also now extinct) that eroded the soil and brought the bones back to the earth’s surface.
“We used a truly multidisciplinary approach (physical and chemical testing) to combine the history of the site,” explained Celina Suarez, a geologist at the University of Arkansas and participating in the study. “The end result [was] that tyrannosaurs died together during a seasonal flood. ”
Members of the BLM research team see their findings as indirect but clear evidence of the group dynamics in action among the Tyrannosaurus rex specimens in question. Their cooperative behavior would have been survival-oriented, focused on group hunting, and perhaps also allow for extended parental attention, scientists say.
“Utah’s new site adds to the growing body of evidence showing that tyrannosaurs were complex, large predators capable of common social behaviors in many of their living relatives, birds,” the research project participant said. Joe Sertich, who is the dinosaur curator at the Denver Museum of Nature and Science. “This discovery should be the turning point for rethinking how these major carnivores behaved and hunted in the northern hemisphere during the Cretaceous.”
A family of fleeing Tyrannosaurus rex dinosaurs. ( Orlando Florin Rosu / Adobe Stock)
Slow and steady he wins the race
Previous evidence supporting the thesis that the Tyrannosaurus rex hunted in packs emerged in 2020, when Canadian scientists published the results of their study on the physiology and anatomy of the tyrannosaurus in the May issue of the journal. PLOS One .
Contrary to previous claims, which claimed that the Tyrannosaurus rex could travel at speeds of up to 70 kilometers per hour, Canadian researchers concluded that a T. rex sprint would not have been able to exceed 12 kilometers per hour. time mark (20 kilometers per hour). The anatomy of T. rex would have allowed them to continue at this speed for considerable distances, however, according to McGill University professor Hans Larsson.
“If this were your hunting mode, be able to travel much greater distances to pretty well [but not great] clip, what kind of lifestyle would it be? The animals that do this today are some, like wolves, that hunt in herds, ”Larsson said.
It is also worth mentioning that the bone bed found in southern Utah is not the first massive Tyrannosaurus rex tomb discovered on the 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 yet another massive T. rex burial was unearthed a few years later in Montana.
If the package hypothesis is true, more such discoveries are certainly expected.
Tyrannosaurus rex attacking an Einiosaurus. ( Elenarts / Adobe Stock)
Imagining countless packs of famous T. Rexes on the hunt
If Tyrannosaurus rex hunted in teams, as suggested by the growing body of evidence, their group cohesion would have given them evolutionary advantages that would have been reflected in their population.
During his 2.5 million year reign as king of the dinosaurs, the powerful Tyrannosaurus rex was always the predator and never the prey. Consequently, there would have been little evidence of its population growth, other than the occasional food shortage (which was probably rare in a prehistoric land full of animal life).
Which begs an interesting question: exactly how many specimens of Tyrannosaurus rex lived and died on the American continent, before the whole species became extinct about 65 million years ago?
A team of scientists and science students from the University of California-Berkeley set out to find the answer to this intriguing query. They collected all the data on the Tyrannosaurus rex that have been obtained from the fossil record and used this information to calculate the half-life of T. rex, along with the nutritional needs of the creature and its likely reproductive capacity.
After expressing all the figures, the Cal-Berkeley team determined that there would have been approximately 20,000 individual animals living in the 1.4 million square kilometers (2.3 million square kilometers) of available habitat space. at the same time. They estimated that a new generation would be born every 19 years and that there would have been approximately 127,000 generations of T. rex over its 2.5 million year lifespan.
If these estimates are correct and scientists claim that it is 95 percent true, it means that 2.5 billion tyrannosaurus reefs lived and died on this planet. If they traveled in groups of 10 to 20, between one and two thousand packets of T. rex would have been roaming the continent looking for food at all times.
Assuming that was the case, the animals that T. rex preyed on would have enjoyed precious moments of tranquility. As soon as a thundering herd of the most terrifying predator the planet has ever produced had passed, another one from the horizon would soon arrive and that new herd would be as devouring as the one that had preceded it.
If humans ever perfected the science of time travel, we should probably think twice about visiting the American continent during the late Cretaceous.
Top image: Tyrannosaurus rex, according to the latest scientific study, hunted in packs, like wolves. Source: warpaintcobra / Adobe Stock
By Nathan Falde