Great whites may have doomed the largest shark that ever lived, fossil teeth reveal | CNN


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Megalodon, the giant shark that lived over 23 million years ago and inspired the movie “The Meg”, was almost four times larger than the great white shark that cruises our oceans today.

However, the two shark species, which once co-existed, likely hunted some of the same prey. This competition could potentially have been one of the reasons the 65-foot-long (20-meter-long) megalodon became extinct, according to a new study.

To arrive at this discovery, the researchers involved in the study used a new technique. They analyzed the food signatures in the teeth of 13 extinct shark species and 20 modern sharks to understand where they are in the food chain – also known as the trophic level.

“Megalodon is usually portrayed as a monstrous, large shark in novels and movies, but the reality is that we still know very little about the extinct shark,” said study author Kenshu Shimada, a professor of paleobiology at DePaul University in Chicago and research fellow at the Sternberg Museum of Natural History in Kansas.

“Our new study shows that the food range of the early Pliocene great white shark is very similar to that of megalodon, indicating that our data does not contradict the competition hypothesis,” he said via email. mail.

The researchers were able to glean this information by examining the presence of different isotopes, or variants, of the chemical element zinc conserved in sharks. dental enamel.

Zinc is essential for living organisms and plays a crucial role in bone development. The ratio of heavy and light zinc isotopes in teeth keeps a record of the type of animal matter that sharks have eaten.

“Zinc isotopes can be used as ecological indicators because of the ratio of these two different isotopes that change as you move up the food chain,” said co-author Michael Griffiths, a geochemist and professor in the Department of Science at the environment. at William Paterson University in New Jersey.

For example, if megalodon ate great white sharks, its higher position in the food chain would be reflected in the isotopic record. But the study found that both species had some overlap, suggesting that they shared similar prey. However, the authors cautioned that they cannot rule out megalodon feeding on great whites, given that its isotopic values, and in particular a close relative of megalodon, called Chubutensis megalodon, had lower values ​​than any modern marine vertebrate and measured fossil..

Feeding at the same trophic level does not necessarily imply direct competition between megalodon and great white sharks for the same prey, as the two species could have specialized in different prey. However, at least some food overlap between the two species was likely, according to the study.

“Like the great whites today, they probably fed on large fish. The smaller-sized great whites probably didn’t need as much food as the megalodon, so they would have had the competitive edge if they were feeding on similar prey,” Griffiths said via email.

The research was published Tuesday in the journal Nature Communications.

This study was the first time that diet-bound zinc isotopes were proven to be preserved in fossilized shark teeth.

A similar technique, using nitrogen isotopes to study the dietary signatures of other groups of animals, is well established, according to the study. However, the nitrogen in the dentin of teeth does not retain well enough to study animals that died out millions of years ago.

The technique using zinc isotopes could be applied to other extinct animals to understand their diet and ecology.


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