At any time when paleontologist Dana Ehret provides 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 Pure Historical past on the New Jersey State Museum in Trenton. “Properly,” he says, “no matter it needed.”
Now, there is likely to be proof that’s actually true. Some megalodons (Otodus megalodon) could have been “hyper apex predators,” increased up the meals chain than any ocean animal ever recognized, researchers report within the June 22 Science Advances. Utilizing chemical measurements of fossilized tooth, scientists in contrast the diets of marine animals — from polar bears to historical nice white sharks — and located that megalodons and their direct ancestors have been typically predators on a stage by no means seen earlier than.
The discovering contradicts one other current examine, which discovered megalodons have been at an analogous stage 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.
Within the newest examine, researchers examined dozens of fossilized tooth for kinds of nitrogen, known as isotopes, which have completely different numbers of neutrons. In animals, one particular nitrogen isotope tends to be extra frequent 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 trendy creatures’ diets. However researchers have been nearly by no means capable of apply it to fossils thousands and thousands of years outdated as a result of the nitrogen ranges have been too low. Within the new examine, scientists get round this by feeding their samples to micro organism that digest the nitrogen right into a chemical the staff can extra simply measure.
The end result: Megalodon and its direct ancestors, recognized collectively as megatooth sharks, confirmed nitrogen isotope excesses typically better than any recognized marine animal. They have been on common most likely two ranges increased on the meals chain than right this moment’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 School of Charleston in South Carolina who was not concerned within the examine. “Even when megalodon was consuming nothing however killer whales, it will nonetheless must be getting a few of this extra nitrogen from one thing else,” he says, “and there’s simply nothing else within the ocean right this moment that has nitrogen isotopes which can be that concentrated.”
“I don’t know the right way to clarify it,” he says.
There are potentialities. Megalodons could have eaten predatory sperm whales, although these went extinct earlier than the megatooth sharks. Or megalodons may have been cannibals (SN: 10/5/20).
One other complication comes from the sooner, contradictory examine. These researchers examined the identical meals chain — in some instances, even the identical shark tooth — utilizing a zinc isotope as an alternative of nitrogen. They drew the other conclusion, discovering megalodons have been on an analogous stage as different apex predators.
The zinc methodology shouldn’t be as established because the nitrogen methodology, although nitrogen isotopes have additionally hardly ever been used this fashion earlier than. “It could possibly be that we don’t have a complete understanding and grasp of this method,” says Sora Kim, a paleoecologist on the College of California, Merced who was concerned in each research. “But when [the newer study] is correct, that’s loopy.”
Confirming the outcomes could be a step towards understanding why megalodons died off. If nice whites had an analogous weight-reduction plan, it may imply that they outcompeted megalodons for meals, says Ehret, who was not concerned within the examine. The brand new findings recommend 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 tooth with each methods may remedy the thriller and reconcile the research. On the identical time, Kast says, there’s loads to discover with their methodology for measuring nitrogen isotopes in fossils. “There’s so many animals and so many various ecosystems and time durations,” she says.
Boessenecker agrees. In the case of the traditional oceans, he says, “I assure we’re going to seek out out some actually bizarre stuff.”
