Megatooth sharks could have been greater on the meals chain than any ocean animal ever

At any time when paleontologist Dana Ehret provides talks in regards to 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 Pure Historical past on the New Jersey State Museum in Trenton. “Effectively,” he says, “no matter it wished.”

Now, there may be proof that’s actually true. Some megalodons (Otodus megalodon) could have been “hyper apex predators,” higher up the food chain than any ocean animal ever known, researchers report within the June 22 Science Advances. Utilizing chemical measurements of fossilized enamel, scientists in contrast the diets of marine animals — from polar bears to historical nice white sharks — and located that megalodons and their direct ancestors had been usually predators on a stage by no means seen earlier than.

The discovering contradicts one other current research, which discovered megalodons had been at an analogous stage within the meals chain as great 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.

Within the newest research, researchers examined dozens of fossilized enamel for kinds of nitrogen, referred to 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 study fashionable creatures’ diets. However researchers had been virtually by no means in a position to apply it to fossils hundreds of thousands of years previous as a result of the nitrogen ranges had been too low. Within the 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 outcome: 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 greater on the meals chain than immediately’s nice white sharks, which is like saying that some megalodons would have eaten a beast that ate nice whites.

“I positively thought that I’d simply tousled within the lab,” says Emma Kast, a biogeochemist on the College of Cambridge. But on nearer inspection, the information held up.

The result’s “eyebrow-raising,” says Robert Boessenecker, a paleontologist on the Faculty of Charleston in South Carolina who was not concerned within the research. “Even when megalodon was consuming nothing however killer whales, it might nonetheless have to be getting a few of this extra nitrogen from one thing else,” he says, “and there’s simply nothing else within the ocean immediately that has nitrogen isotopes which are that concentrated.”

“I don’t know find out how to clarify it,” he says.

There are prospects. Megalodons could have eaten predatory sperm whales, although these went extinct earlier than the megatooth sharks. Or megalodons could have been cannibals (SN: 10/5/20).  

One other complication comes from the sooner, contradictory research. These researchers examined the identical meals chain —  in some circumstances, even the identical shark enamel — utilizing a zinc isotope as an alternative of nitrogen. They drew the alternative conclusion, discovering megalodons had been on an analogous stage as different apex predators.

The zinc technique will not be as established because the nitrogen technique, although nitrogen isotopes have additionally not often been used this manner earlier than. “It may very well be that we don’t have a complete understanding and grasp of this system,” says Sora Kim, a paleoecologist on the College of California, Merced who was concerned in each research. “But when [the newer study] is true, that’s loopy.”

Confirming the outcomes could be a step towards understanding why megalodons died off. If nice whites had an analogous food plan, it may imply that they outcompeted megalodons for meals, says Ehret, who was not concerned within the research. The brand 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 remedy the thriller and reconcile the research. On the similar time, Kast says, there’s loads to discover with their technique for measuring nitrogen isotopes in fossils. “There’s so many animals and so many alternative ecosystems and time durations,” she says. 

Boessenecker agrees. With regards to the traditional oceans, he says, “I assure we’re going to seek out out some actually bizarre stuff.”

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