About 2.5 billion T. Rex dinosaurs trampled on Earth’s surface, study finds

Christie's exhibits Tyrannosaurus Rex skeleton known as Stan before auction

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Only about 100 Tyrannosaurus rex fossils have been discovered since the species was first described by American paleontologist Henry Fairfield Osborn in 1902. Species of carnivorous dinosaurs T. rex lived approximately 66 to 68 million years ago during the Cretaceous Period in the western United States, including Montana and Wyoming.

But how many alive T. rex individuals roaming the earth during this period?

Paleontologists led by Charles Marshall of the University of California at Berkeley used a method employed by environmentalists who study contemporary creatures to estimate the population density of extinct species. What the team found, published this week in the journal Science, is that around 20,000 adults T. rex individuals have probably lived at some point, giving or taking a factor of 10.

The population density of living animals is related to their body size (mass) and the geographic extent (and available resources) they occupy – this is called Damuth’s law. Damuth’s law states that the average population density of a species predictably decreases as body mass increases; for example, the same area can accommodate a few elephants, but a large number of mice.

“The project just started out like a lark, in a way,” Marshall said. “When I hold a fossil in my hand I can’t help but wonder how alive this beast was millions of years ago, and here I’m holding part of its skeleton – it seems so improbable . The question kept popping up. in my head: “How improbable is that?” Is it one in a thousand, one in a million, one in a billion? And then I started to realize that maybe we could estimate how many were alive, and so I could answer that question. ”

The team used their estimates of the total range of T. rex across modern North America, combined with their estimates of dinosaur body mass, to calculate the absolute abundance and conservation rate of the T. rex population. The authors quickly point out that the uncertainties in the estimates are significant. While the population was probably 20,000 adults at all times, the 95% confidence range – the population range in which there is a 95% chance that the true number will be found – is 1,300 to 328,000 individuals. . The total number of individuals that have existed during the life of the species could have been between 140 million and 42 billion.

The name of T. rex the number of individuals represented in museums and in the hands of private collectors is of the order of 100 individuals, including 32 adults. The result is a fossil specimen recovered from 80 million animals that have never lived. These figures confirm an old rule in paleontology – that fossils in general are extremely rare, and suggest that many species that once lived on Earth have probably never been preserved.

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