In a study published today in the journal Earth and Planetary Science Letters, paleontologists analyzed the ratio of two different zinc isotopes in the dental enamel of 19 species from an Early Miocene marine ecosystem, including the megatooth sharks Otodus megalodon and Otodus chubutensis.
Otodus megalodon went extinct 3.6 million years ago. Image credit: Alex Boersma / PNAS.
Otodus megalodon was a gigantic megatooth shark that lived in the world’s oceans from 23 to 3.6 million years ago.
It could grow to the enormous size of at least 15 m long, making it one of the largest apex marine predators since the Mesozoic.
“Otodus megalodon swam through the world’s oceans between 23 and 3 million years ago, frequently on the hunt for prey to satisfy a calorie demand as vast as its size,” said Goethe University Frankfurt’s Dr. Jeremy McCormack and colleagues.
“According to estimates, it required around 100,000 kilocalories per day.”
“Scientists widely assumed that megalodon’s main calorie intake was in the form of whales.”
“At least that’s what it did should a whale come long.”
“It appears, after all, that megalodon had a much broader range of prey than previously assumed.”
In the new study, Dr. McCormack and co-authors analyzed the ratio of zinc-64 and zinc-66 isotopes in the dental enamel of 19 fossil species from 20.4- to 16-million-year-old sediments deposited in a shallow seaway (Burdigalian Seaway) in what is now southern Germany.
“Zinc is ingested with food, whereby less of the heavier isotope zinc-66 than the lighter isotope zinc-64 is stored in muscles and organs,” they explained.
“Accordingly, the tissue of fish that eat fish absorbs significantly less zinc-66, and those which, in turn, hunt them for food absorb even less.”
“That is why Otodus megalodon and its close relative Otodus chubutensis had the lowest ratio of zinc-66 to zinc-64 at the top of the food chain.”
“Sea bream, which fed on mussels, snails and crustaceans, formed the lowest level of the food chain we studied,” Dr. McCormack said.
“Smaller shark species such as requiem sharks and ancestors of today’s cetaceans, dolphins and whales, were next.”
“Larger sharks such as sand tiger sharks were further up the food pyramid, and at the top were giant sharks like Araloselachus cuspidatus and the Otodus sharks, which include megalodon.”
“However, the Otodus sharks cannot be sharply differentiated from the lower levels of the pyramid.”
“Megalodon was by all means flexible enough to feed on marine mammals and large fish, from the top of the food pyramid as well as lower levels — depending on availability.”
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Jeremy McCormack et al. Miocene marine vertebrate trophic ecology reveals megatooth sharks as opportunistic supercarnivores. Earth and Planetary Science Letters, published online May 26, 2025; doi: 10.1016/j.epsl.2025.119392
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