Estimating the maximum height of our species by looking at a single human would not yield very realistic results. Why shouldn’t it be true for other animals? How can we know the maximum size of, say, a T. rex when we have less than a hundred skeletons to base our observations on? In fact, according to a new study published in the journal Ecology and Evolution, the largest T. rexes that ever lived may have reached much, much larger sizes than any found to date.
The research, conducted by paleobiologist Jordan Mallon of the Canadian Museum of Nature and paleontologist David Hone of Queen Mary University of London, starts from the recognition of the fact that the fossil remains of now extinct animals cannot represent a faithful testimony of the maximum and minimum dimensions that a species could reach. It is only chance, after all, that establishes which specimens will be preserved as fossils, and which of these will then be discovered by paleontologists. And the probability of discovering the remains of one of the largest specimens of a given species that ever lived is close to zero: looking at tyrannosaurs, for example, just over 80 reasonably complete skeletons have been discovered, compared to at least two and a half billion specimens that have inhabited our planet in about 2.4 million years.
Knowing the maximum and minimum dimensions of an animal species is very useful for carefully reconstructing its habits and the ecological niche it occupied, and can also help study its evolutionary path. For this reason, the two scientists decided to try to estimate more precisely the maximum size that T. Rex could have reached before becoming extinct. To do so, they created a computer model, with which they simulated over 140 million specimens of tyrannosaurus based on all the information available on this species, such as population size, growth rate, lifespan, and so on.
In this way, using their virtual population of T. Rex, the two were able to assess how representative the skeletons found to date are of the maximum dimensions of these dinosaurs. And the answer is that most likely the largest skeleton ever discovered, that of a specimen unearthed in 1991 in Canada and known by experts as “Scotty,” which reached nearly 9 tons in weight according to the most credible estimates, belonged to one of the largest specimens ever to exist, larger in size than about 99% of its conspecifics.
It remained to be seen, however, what size the 1% of tyrannosaurs larger than Scotty could have reached. According to the model, specimens of 13, or even 15 tons could have been reached, for a total length that could have exceeded 15 meters. These are estimates, of course, and it is therefore impossible to say with certainty whether such a giant ever walked on our planet. Even if it had happened, however, the two researchers estimate that at least another thousand years of excavations would be needed to have any hope of finding a fossil of such a unique specimen.
For this reason, the two invite us to consider their results with a healthy dose of skepticism: the demonstration that in reality, it is almost impossible to establish with precision the size of an extinct species based on the few fossils that we manage to find. “It is important to underline that this is not only true for T. Rex, on which we based our research, but it is a question that applies to all dinosaurs and many other fossil species,” Hone emphasizes. “Arguing who is the biggest based on a handful of skeletons actually doesn’t make much sense.”