Analysis of zinc isotopes in the teeth of ancient sharks suggests that megalodon and great whites ate the same foods, potentially contributing to the mysterious extinction of megalodon
May 31, 2022
A prehistoric food battle may help explain the mysterious disappearance of the megalodon, the world’s largest shark. He may have found himself in a losing battle for prey with large whites, suggests an analysis of zinc in the ancient tooth enamel of both shark species.
About 3.5 million years have passed since the death of the last megalodon, but the cause of death of the giant predator remains a mystery. Previous research has shown that megalodon may have struggled to find enough food to satisfy its huge appetite, and Kenshu Shimada at DePaul University, Illinois, and his colleagues were eager to learn more about the place of the giant fish in the food chain.
Megalodon’s approximately 15-meter body contained a skeleton made of cartilage – which does not petrify well – so researchers are left with the teeth of palm-sized animals to give clues as to how it lived.
“My collaborators and I wanted to see if we could decipher the diet of megalodon and other extinct sharks, including the prehistoric great white shark, using zinc isotopes preserved in petrified teeth,” Shimada said.
This is the first time scientists have used zinc isotope analysis on shark teeth, but the technique has been found to be “a powerful tool for deciphering relative positions in the food chain among different species,” Shimada said.
Using a drill to collect tooth enamel, the team took samples of 20 live shark species and 13 extinct species, including megalodon. They then compared the different levels of zinc retained in 262 individual teeth. Zinc is essential for the life of animals and is obtained mainly from food – with the right balance of zinc isotopes in food, and hence the tooth enamel, which is indicative of the type of food that the animal ate.
Researchers have found that the ratio of zinc isotopes in the megalodon sample is very similar to that of the ancient great white sharks. Because both species had low levels of zinc in their tooth enamel, they probably shared a similar position as a predator on top in the early Pliocene, about 5 million years ago, when the two coexisted.
Shimada notes that previous evidence of fossilized bite marks points to the fact that large whites and megalodon may have shared a diet of small whales, seals and sea lions. Although there may have been many reasons for the megalodon’s disappearance, Shimada said he was “very excited” to see that their study offered more evidence that competition for food with large whites was a factor.
Reference journal: Natural communications, DOI: 10.1038 / s41467-022-30528-9
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