For the first time, scientists have estimated how much Tyrannosaurus rex, the so-called king of dinosaurs, once roamed the earth.
Why it matters: The number is staggering: 2.5 billion Tyrannosaurus rex lived and died during the approximately 2.4 million years that the species survived on the planet, according to a new study to be published in the journal. Science on Friday.
The study according to lead researcher Charles Marshall, director of the University of California Museum of Paleontology, it may help to contextualize the fossil record and the rarity of finding fossilized prehistoric organisms.
- “I mean, for me, it’s just great that we could come up with a number,” Marshall told Axios. Some people have asked me, ‘How do you compare your number to other numbers of the total who ever lived? ‘The answer is that it is not, because there was not. ‘
How it works: The team of researchers could not use the limited fossil record to estimate the population of the species, and so used Damuth’s Law, which describes a relationship between population density and body mass.
- The bandage, used in population ecology, generally says that species with larger body size tend to have lower population densities.
- The researchers then calculated the average body mass of a T. rex, averaging 5,200 kilograms (about 11,460 pounds).
- Using the body mass and population density, the team calculates that the species has a population density of about one individual per 40 square miles.
By the numbers: With this information and an estimated geographic area that the species occupies, the researchers were able to approximate that about 20,000 T. rex live at any given time that the species lived on the planet.
- To find the total number of T. rex that walked the earth, the team multiplied the permanent population of the species by the number of genera it covered (about 127,000), which they determined by dividing by species has survived through its estimated generation time of 19 years.
- The researchers noted that their estimated population density for the species would translate to about 3,800 T. rex in an area the size of California and only two in an area the size of Washington, DC
Yes, but: Marshall said the accuracy of the analysis was’ low ‘and this was mainly due to uncertainty about the accuracy of the relationship between live animals’ body mass and their population density, rather than to the paleontological data the team used.
James Clark, a professor of biology at George Washington University, who did not participate in the study, said the research did not come to a definitive conclusion, but that it was difficult to estimate the lives of extinct animals. .
- “It’s an exercise in what you can and cannot tell,” Clark said. “It gives you a chance to say, ‘Wow, there really were a lot of these things, and we do not get much of them trapped in the fossil record.’
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