Whenever paleontologist Dana Ehret offers talks concerning the 15-meter-long prehistoric sharks generally known as megalodons, he likes to make a joke: “What did megalodon eat?” asks Ehret, Assistant Curator of Natural History on the New Jersey State Museum in Trenton. “Well,” he says, “whatever it wanted.”
Now, there is likely to be proof that’s actually true. Some megalodons (Otodus megalodon) might have been “hyper apex predators,” larger up the meals chain than any ocean animal ever identified, researchers report within the June 22 Science Advances. Using chemical measurements of fossilized enamel, scientists in contrast the diets of marine animals — from polar bears to historic nice white sharks — and located that megalodons and their direct ancestors had been usually predators on a degree by no means seen earlier than.
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The discovering contradicts one other latest research, which discovered megalodons had been at the same degree within the meals chain as nice white sharks (SN: 5/31/22). If true, the brand new outcomes would possibly change how researchers take into consideration what drove megalodons to extinction round 3.5 million years in the past.
In the newest research, researchers examined dozens of fossilized enamel for types of nitrogen, known as isotopes, which have totally different numbers of neutrons. In animals, one particular nitrogen isotope tends to be extra widespread than one other. A predator absorbs each when it eats prey, so the imbalance between the isotopes grows additional up the meals chain.
For years, scientists have used this development to find out about fashionable creatures’ diets. But researchers had been nearly by no means in a position to apply it to fossils thousands and thousands of years previous as a result of the nitrogen ranges had been too low. In the brand new research, scientists get round this by feeding their samples to micro organism that digest the nitrogen right into a chemical the workforce can extra simply measure.
The consequence: Megalodon and its direct ancestors, identified collectively as megatooth sharks, confirmed nitrogen isotope excesses typically higher than any identified marine animal. They had been on common most likely two ranges larger on the meals chain than as we speak’s nice white sharks, which is like saying that some megalodons would have eaten a beast that ate nice whites.
“I definitely thought that I’d just messed up in the lab,” says Emma Kast, a biogeochemist on the University of Cambridge. Yet on nearer inspection, the info held up.
The result’s “eyebrow-raising,” says Robert Boessenecker, a paleontologist on the College of Charleston in South Carolina who was not concerned within the research. “Even if megalodon was eating nothing but killer whales, it would still need to be getting some of this excess nitrogen from something else,” he says, “and there’s just nothing else in the ocean today that has nitrogen isotopes that are that concentrated.”
“I don’t know how to explain it,” he says.
There are potentialities. Megalodons might have eaten predatory sperm whales, although these went extinct earlier than the megatooth sharks. Or megalodons may have been cannibals (SN: 10/5/20).
Another complication comes from the sooner, contradictory research. Those researchers examined the identical meals chain — in some instances, even the identical shark enamel — utilizing a zinc isotope as an alternative of nitrogen. They drew the other conclusion, discovering megalodons had been on the same degree as different apex predators.
The zinc technique isn’t as established because the nitrogen technique, although nitrogen isotopes have additionally hardly ever been used this manner earlier than. “It could be that we don’t have a total understanding and grasp of this technique,” says Sora Kim, a paleoecologist on the University of California, Merced who was concerned in each research. “But if [the newer study] is right, that’s crazy.”
Confirming the outcomes can be a step towards understanding why megalodons died off. If nice whites had the same weight loss plan, it may imply that they outcompeted megalodons for meals, says Ehret, who was not concerned within the research. The new findings counsel that’s unlikely, however depart room for the likelihood that nice whites competed with — or just ate — juvenile megalodons (SN: 1/12/21).
Measuring extra shark enamel with each strategies may clear up the thriller and reconcile the research. At the identical time, Kast says, there’s a lot to discover with their technique for measuring nitrogen isotopes in fossils. “There’s so many animals and so many different ecosystems and time periods,” she says.
Boessenecker agrees. When it involves the traditional oceans, he says, “I guarantee we’re going to find out some really weird stuff.”