Billions of T. rex likely roamed the Earth, paleontologists report


If you traveled back in time 67 million years ago to ancient Montana, you would be entering the realm of a tyrant – the iconic predator. Tyrannosaurus Rex. However, before venturing into that lost world, you may want to know: on average, how close is the closest Tyrant Saurus Rex for you?

That may sound like an impossible thing to know, but after analyzing the value of two decades of Tyrant Saurus Rex research, a new study provides estimates of the animal’s population density. In all likelihood, a Tyrant Saurus Rex it would be 15 miles from you, if not much closer.

The new study, published last Thursday in Sciences, also translates these population densities into estimates of how many Tyrant Saurus Rex ever lived. On average, researchers estimate that about 20,000 Tyrant Saurus Rex lived at any one time and that around 127,000 generations of dinosaurs lived and died. Those averages imply that a total of 2.5 billion Tyrant Saurus Rex lived in the species’ native North America, possibly as far north as Alaska and as far south as Mexico, for a period of two to three million years.

This research is not the first time that scientists have tried to estimate Tyrant Saurus Rex numbers. In fact, the average population density in the new paper, roughly one Tyrant Saurus Rex every 42 square miles, closely resembles an earlier estimate published in 1993. But the new study uses the latest Tyrant Saurus Rex research in biology to try to establish high precision upper and lower limits on the total population.

After running millions of computer simulations, each with a slightly different combination of possible values, the study found that the total Tyrant Saurus Rex the count could be as low as 140 million and as high as 42 billion, averaging around 2.5 billion. Similarly, between 1,300 and 328,000 Tyrant Saurus Rex he could have been alive at any time, with an average of 20,000.

“It’s really exciting that someone is trying to … use everything we know about Tyrant Saurus Rex to try to figure out population dynamics, “says Holly Woodward, a paleontologist at the Oklahoma State University Health Sciences Center who was not involved in the new study. “It’s interesting and fun that this was not done on this kind of scale.” (Learn more about Woodward’s research on how Tyrant Saurus Rex passed his adolescence.)

Tyrant Saurus Rex accounting

In the past 20 years, researchers have discovered an extraordinary number of Tyrant Saurus Rex, including how long he lived (approximately 28 years), when he reached sexual maturity (approximately 15.5 years), and how much he weighed when fully developed (approximately 15,000 pounds, on average). These data allow scientists to calculate Tyrant Saurus Rexthe approximate generation time (19 years or so) and the average body mass of Tyrant Saurus Rex at any given time.

To get to Tyrant Saurus RexBased on the population figures, the researchers took advantage of the relationship between body mass and population density among living animals. On average, as body mass increases by a factor of 10, population density decreases by more than four fifths, a pattern known as Damuth’s Law.

Damuth, an ecologist at the University of California, Santa Barbara, first discovered this pattern by compiling 30 years of ecological data on living mammals. However, Damuth’s Law is not rigid, as animals vary widely in their specific lifestyles and habitats. For example, spotted hyenas and jaguars have similar body masses, and both are predators, but the population density of hyenas is about 50 times higher.

When applied to Tyrant Saurus Rex (after correcting the fact that Tyrant Saurus Rex not a mammal), Damuth’s Law implied that the true total of the dinosaur was probably between 140 million and 42 billion individual dinosaurs.

“In paleontology, it’s very difficult to estimate things … so what I started to do is think less about estimating something and more about putting it in square brackets. Can I put a robust upper and lower limit on it? “says study lead author Charles Marshall, a paleontologist at the University of California, Berkeley.

From life to rock

In addition to getting a better idea of ​​how many of these elephant-sized predators were stomping around, Marshall and his team were able to calculate the numbers to better estimate how often fossils form. Could the odds of a Tyrant Saurus Rex quantify fossilization, in the same way that we can calculate the probabilities of being struck by lightning?

There are a hundred known specimens of Tyrant Saurus RexBut about two-fifths of them are in private or commercial hands and cannot be reliably studied. So, to establish a minimum fossil total for the purposes of the study, Marshall’s team limited their count to 32 post-juvenile fossil fossils. Tyrant Saurus Rex that are carried out in public institutions.

If all the Tyrant Saurus Rex that ever lived, the estimated 2.5 billion, produced just those 32 fossils, then just one in 80 million Tyrant Saurus Rex fossilized after his death. Even if a higher percentage of the animals were fossilized and the remains have yet to be found, the smallness of these probabilities underscores how rare it is for a corpse to be buried fast enough and under the right chemical conditions to mineralize and form a fossil. . “Yes Tyrant Saurus Rex they were a thousand times less abundant, if the total were not 2,500 million, but 2,500 million million“We may never have found it,” says Marshall.

The method Marshall’s team has described could also be used for other extinct creatures. Among dinosaurs, researchers say one of the best candidates is the Cretaceous herbivore. Maiasaura, which is known from hundreds of specimens, from newborn to adult.

For Woodward, one of the most exciting implications of the study is how rare dinosaur fossils really are. If these rates are valid for species other than Tyrant Saurus Rex, researchers can even estimate how many species of dinosaurs simply weren’t fossilized at all, and are now irrevocably lost in time. “Being able to figure out how much we lack can be as important as knowing how much we have,” he says.



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