Updated:01/06/2022 12:05h
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The megalodon, the largest shark of all time, roamed Earth’s oceans for millions of years. Up to 20 meters long, three times the size of today’s largest white shark, it became one of the most fearsome predators that ever lived until its extinction some 3.6 million years ago. Why such a fabulous animal disappeared, a true killing machine, remains a paleontological mystery. Multiple explanations have been given. One of them linked the death of the carnivore, and that of other marine species, with the explosion of a supernova. And even the idea spread, refuted by scientists, that the megalodon is still alive.
A study published in the scientific journal ‘Nature Communications’ proposes a new hypothesis. Its authors, an international team of researchers, believe that what ended the fantastic megalodon (Otodus megalodon) was the competition for food. As they explain, the appearance of white sharks, also at the top of the food chain, could have put unbearable pressure on the primitive beast, which saw its prey diminished.
The key to this conclusion lies in the teeth of the predators. The researchers analyzed the stable isotope ratios of zinc in the tooth enamel of modern and fossil sharks from around the world, including megalodon and great white sharks. This is a new method that allows scientists to investigate where an animal is in the food chain. That is, who eats whom.
The new analysis is comparable to a more traditional one, that of nitrogen isotopes of dental collagen, the organic tissue in dentin, which is used to assess the degree of consumption of animal matter. However, “on the time scales we investigated, collagen is not conserved and therefore cannot be used,” explains Jeremy McCormack, lead author of the study and a researcher at the Max Planck Institute for Evolutionary Anthropology and the University Goethe of Frankfurt. “Here, we show, for the first time, that diet-related zinc isotope signatures are preserved in the highly mineralized enameled crown of fossil shark teeth,” adds Thomas Tütken, Professor at the Institute of Geosciences at Johannes Gutenberg University. .
In this way, the team compared the dental zinc isotope signature of multiple extinct species from the early Miocene (from 20.4 to 16.0 million years ago) and the early Pliocene (from 5.3 to 3.6 million years ago). ) with those of modern sharks.
The researchers then analyzed zinc isotope ratios in megalodon teeth from the early Pliocene and earlier megatoothed sharks, Otodus chubutensis early Miocene, as well as contemporary and modern great white sharks to investigate the impact these iconic species had on past ecosystems.
“Our results show that both megalodon and its ancestor were predators high up in their respective food chains,” says Michael Griffiths, a professor at William Paterson University. “But what was really remarkable is that the zinc isotope values of early Pliocene shark teeth (found) in North Carolina suggest largely overlapping trophic levels of early great white sharks with the much larger megalodon.” .
dietary competition
“These results likely imply at least some overlap in the prey taken by both shark species,” says Kenshu Shimada, a professor at DePaul University in Chicago. “While additional research is needed, our results appear to support the possibility of megalodon dietary competition with great white sharks.”
According to the researchers, new isotope methods such as zinc provide a unique window into the past. “Our research illustrates the feasibility of using zinc isotopes to investigate the diet and trophic ecology of extinct animals over millions of years, a method that can also be applied to other groups of fossil animals, including our own ancestors,” McCormack concludes.
These sharks shed thousands of teeth throughout their lives, which is why they have left numerous traces in the fossil record. New surprises are likely to lie ahead that help describe what that animal was really like beyond how it appears in consumer popcorn movies.
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