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Tyrannosaurus_Rex_Holotype-Feature

All that remains of the Tyrannosaurus rex today is a handful of fossils, just how many of these iconic dinosaurs roamed the Earth? A new analysis from the Academy of California Berkeley estimates that at that place were about 20,000 adult Tyrannosaurs at any given fourth dimension during the Cretaceous flow. Add that up over millions of years, and there could easily have been two.5 billion of these dinosaurs in full.

Paleontologists have unearthed just 32 adult T. rex fossils, which is not enough to estimate their range or numbers. Fossils tell the states most individual animals — how they lived, how they died, and how they were built. So few animals become fossils that y'all tin't tell how large a population was just from how many bones are in the ground. However, knowing most the fauna'southward biological science can help make an gauge of population, as long equally you lot're not looking for an exact headcount.

The researchers, led by Berkeley biology professor Charles Marshall, used tools designed for modern animals to analyze the dinosaur. The core premise of the piece of work is that in that location is a consistent relationship betwixt large and pocket-size animals. For instance, in that location are more rats than there are elephants. We can't say for sure that the human relationship was the same in the Cretaceous, but it's at least plausible.

For the animals of today, Academy of California Santa Barbara scientist John Damuth developed a concept called Damuth'southward law that uses an brute's body mass to guess population density. This calculation has held true for almost large carnivorous animals alive today, merely it does vary based on factors like metabolism. Scientists no longer believe dinosaurs were cold-blooded, just they weren't fully homeothermic animals similar modern mammals. So, the team used a value between a mammal and Komodo dragons.

A Tyrannosaurus male monarch known every bit "Sue" at Chicago's Field Museum. Credit: Ryan Whitwam

That's how we go to twenty,000 adult Tyrannosaurs sharing the Earth at any one time. The number could accept been much college or lower, of course. The calculation shows that 20,000 is the nigh likely value, only it could have been as low every bit one,300 or every bit loftier as 328,000. The team reports a 97.5 percent probability the real number was between those two values. This was all earlier information technology dropped to zero following an asteroid impact some 65 million years agone.

Marshall himself believes the population was higher, and nosotros just don't have the information to bear witness it. Damuth'south law doesn't piece of work for every species. Jaguars and hyenas are roughly the same size, but the population density for hyenas is well-nigh 50 times higher. Nosotros might never know how many Tyrannosaurs roamed the Earth, but a precious few were preserved for humans to discover. The new study estimates just 1 in every fourscore meg Tyrannosaurs fossilized.

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