North American paleontologists estimate Earth has been home to 2.5 billion Rex tyrannosaurs in its history

2.5 billion of King Tiranosaurios it is a large number. This figure is what North American paleontologists arrived at, based on their calculations of the existence of one of the most powerful predators on the planet.

The study reveals that probably around 20,000 ‘T. rex ‘adults at any time, plus or minus a factor of 10, which is what most researchers have assumed. What few paleontologists fully understand, according to lead researcher Charles Marshall, is that this means that some 2.5 billion lived and died for approximately 2 and a half million years that the dinosaur walked on Earth.

“The project started out, sort of like a joke,” said Marshall, director of the University of California Museum of Paleontology, Philip Sandford Boone, chair of paleontology and professor of integrative biology and human sciences. earth and planets. From UC Berkeley-. VShen I have a fossil in my hand, I can’t help but wonder about the improbability that this same beast was alive millions of years ago, and here I am holding part of his skeleton … it seems so improbable. The question that comes to my mind is, “Is it unlikely?” Is it one in a thousand, one in a million, one in a billion? And then I started to realize that maybe we can estimate how many were alive and so I could answer that question. “

Until now, no one had been able to calculate the numbers of long-extinct animals.

Marshall explained that the uncertainties in the estimates are significant. While the population of ‘T. rex ‘is probably 20,000 adults at a time, 95% confidence interval -the segment of the population in which there is a 95% chance that the real number will be found- is 1300 to 328000 individuals. Therefore, the total number of individuals that have existed throughout the life of the species could have been between 140 million and 42,000 million.

“In our study, we focused on developing strong constraints on the variables we needed to do our calculations, rather than focusing on the best estimates,” said the specialist.

The greatest uncertainty in these numbers, Marshall noted, centers on questions regarding the exact nature of the dinosaur’s ecology, including the degree of T. rex ‘. The study is based on data published by John Damuth of the University of California at Santa Barbara, which relate body mass to the population density of living animals, a relationship known as Damuth’s law.

While the relationship is strong, remember, ecological differences result in large variations in the population densities of animals with the same physiology and ecological niche. For example, jaguars and hyenas are roughly the same size, but hyenas are found in their habitat 50 times the density of jaguars in their habitat.

“Our calculations depend on this relationship for living animals between their body mass and population density, but the uncertainty in the relationship spans about two orders of magnitude. Surprisingly, the uncertainty of our calculations is dominated by this ecological variability and not by the uncertainty of the paleontological data that we use, ”said Marshall.

The question of the place occupied by the “T. rex ‘in the ecosystem has led researchers to ignore juvenile specimens, which are under-represented in the fossil record and who, in fact, could have lived separately from adults and hunted different prey. Like the ‘T. rex ‘has reached maturity, its jaws have strengthened by an order of magnitude, which allowed him to crush bones. This suggests that the juveniles and adults ate different prey and were almost like different predator species.

This possibility is supported by a recent study, led by evolutionary biologist Felicia Smith of the University of New Mexico, which hypothesizes that the absence of medium-sized predators alongside the enormous’ T. The rex predator at the end of the Cretaceous is due to the juveniles occupying this ecological niche.

Scientists at UC Berkeley extracted data from the scientific literature and the experience of their colleagues to estimate the likely age of sexual maturity of a “T. rex ‘was 15.5 years old; its maximum lifespan was probably until the late 1920s; and his average adult body mass – his so-called ecological body mass – was about 5,200 kilograms, or 5.2 tons. They also used data on the speed at which the ‘T. rex ‘grew throughout their lives: they gave a push around sexual maturity and could weigh around 7,000 kilograms.

From these estimates, they also calculated that each generation was around 19 years old, and the average population density was one dinosaur per 100 square kilometers.

Next, estimating that the total geographic range of ‘T. rex ‘was about 2.3 million square kilometers, and as the species survived for about 2.5 million years, they calculated a permanent population of 20,000 people. Out of a total of approximately 127,000 generations that the species has lived, this translates to approximately 2.5 billion individuals in total.

They wondered what, with such a large number of post-juvenile dinosaurs throughout the history of the species, let alone possibly more juveniles, where have all these bones gone? To date, less than 100 individuals have been found, many of which are represented by a single fossilized bone.

“If we limit our analysis of the fossil recovery rate to where the fossils of ‘T. rex ‘are more common, part of the famous Hell Creek formation in Montana we believe we have recovered around one in 16,000 of the “T. rex ‘who lived in this area during this time interval in which the rocks were deposited, ”the researchers said.

“This figure surprised us Marshall acknowledged that this fossil record has a much higher representation of the living than I had expected. It could be as good as one in 1000, if you barely lived there, or it could be as low as one in a quarter of a million, given the uncertainties in the beast’s estimated population densities. “

And closed: “With these numbers we can start to calculate the number of ephemeral and geographically specialized species. we could miss the fossil record. Maybe that’s a way to start quantifying what we don’t know. “

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