An examination of the zinc content of teeth from sharks both living and extinct is providing clues about the demise of the largest-known shark, indicating the mighty megalodon may have been out-competed by the great white shark in ancient seas.
Researchers assessed the ratio of two forms of the mineral zinc in an enamel-like material called enameloid that comprises the outer part of shark teeth. This ratio enabled them to infer the diets of the sharks and gauge their position on the marine food chain.
Megalodon, whose scientific name is Otodus megalodon, appeared about 15 million years ago and went extinct about 3.6 million years ago. It was one of the largest predators in Earth's history, reaching at least 50 feet and possibly 65 feet in length while feeding on marine mammals including whales. "The megalodon co-existed with the great white shark during the time frame called the early Pliocene, and our zinc data suggest that they seem to have indeed occupied the same position in the food chain," said paleobiologist Kenshu Shimada of DePaul University in Chicago, a co-author of the study published on Tuesday in the journal"There have been multiple hypotheses as to why megalodon went extinct.
Today's great white sharks hunt sea turtles as well as marine mammals including seals, sea lions, porpoises, dolphins and small whales.
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