WASHINGTON, May 31 (Reuters) – An examination of the zinc content of shark teeth, both living and extinct, provides clues to the disappearance of the largest known shark, indicating that the powerful megalodon may have been overtaken by the great white shark . in ancient seas.
The researchers evaluated the proportion of two forms of mineral zinc in an enamel-like material called enamel that comprises the outside of shark teeth. This relationship allowed them to infer shark diets and measure their position in the marine food chain.
They found that while the megalodon may have been alone at the top of the food chain for millions of years, the arrival of the great white shark about 5.3 million years ago added another apex predator that hunted similar prey. .
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This food resource contest featured two animals now housed in the popular imagination, with the big white featured in the 1975 hit film “Jaws” and its sequels and the megalodon starring the popular 2018 movie “The Meg”.
Megalodon, whose scientific name is Otodus megalodon, appeared about 15 million years ago and became extinct about 3.6 million years ago. It was one of the largest predators in Earth’s history, reaching at least 50 feet (15 meters) and possibly 65 feet (20 meters) long while feeding on marine mammals including whales.
The great white shark, Carcharodon carcharias, is at least 20 feet (6 meters) long, and may have been the more agile of the two.
“The megalodon coexisted with the great white shark during the time period called the Early Pliocene, and our zinc data suggest that they actually appeared to have occupied the same position in the food chain,” said paleobiologist Kenshu Shimada of DePaul University. of Chicago. , co-author of the study published Tuesday in the journal Nature Communications.
“There have been many hypotheses as to why the megalodon became extinct. Traditional hypotheses have attributed this to climate change and declining food sources. However, a recently proposed hypothesis holds that the megalodon lost competition. “The new white shark has just evolved. Our new study seems to support this proposition. It is also entirely possible that a combination of multiple factors may have been at stake,” Shimada said.
Investigators said the big white is not believed to be really hunting his older cousin.
The study involved teeth from 20 species of live sharks and 13 fossil species, which indicated their position in the food chain.
“At the bottom of the food chain are our ‘primary producers’, which are photosynthetic organisms such as phytoplankton that convert solar energy into food. At the top of the food chain are predators at the apex. like great white sharks, which have no predators except humans, while in between we have lower-level herbivores, omnivores, and carnivores, “said study co-author Michael Griffiths, a geochemist and paleoclimatologist at William Paterson University in New Jersey. .
Today’s great white sharks hunt sea turtles and marine mammals, such as seals, sea lions, porpoises, dolphins, and small whales.
The study indicated that Carcharodon hastalis, considered a direct ancestor of the great white, was not so high up in the food chain, it probably fed on fish instead of marine mammals.
For a creature that played a vital role in marine ecosystems for millions of years, it still remains very mysterious about the megalodon. Because shark skeletons are more cartilaginous than bony, they do not lend themselves well to fossilization, making it difficult to know exactly what the megalodon was like. However, countless fossils of megalodon teeth have been found around the world.
“Megalodon is usually portrayed as a monstrous, oversized shark in novels and movies, but the reality is that we still know very little about this extinct shark,” Shimada said.
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Report by Will Dunham, Edited by Rosalba O’Brien
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