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Twenty million years ago, a predator with a mouth like a subway door and teeth the size of a palm roamed the seas. The largest shark to ever live in the world, the megalodon can grow to over 50 feet and has been a scourge of the ocean for millions of years. Then he disappeared. Megalodon no longer existed.
Exactly what drove this shark monster to extinction is a hotly debated topic among scientists. Now An article published Tuesday in the journal Nature Communications suggests that great white sharks living with megalodon preyed upon the same kinds of animals that much larger sharks ate. This evidence helps support the theory that competition with the great white, a predator that is still vigorous today, may have been a factor that drove the megalodon off the table. It also highlights the idea that a predator need not be the largest to dominate an ecosystem.
Rebuilding the oceans’ food chains has long been a daunting task, said Jeremy McCormack, a geoscientist at the Max Planck Institute for Evolutionary Anthropology in Germany and author of the new paper. You can’t watch extinct animals feed or set up a camera to spy on how they lived.
But there are other methods. One way to understand what an animal eats is to study the molecules that make up its body. Zinc isotope levels in the teeth of modern mammals related to where they fall in the food chain, many other studies have found that the higher an animal is in the food chain, the lower the zinc isotope values they show. Because teeth are well fossilized, the team wondered if the same would be true when they looked at teeth millions of years ago.
Using the teeth of more than a hundred sharks, drawing from species living today and long ago, the researchers ran tests to see if zinc levels changed as the teeth wore off. They also confirmed that zinc isotope values in present-day sharks reflect their place in the ecosystem – for example, sharks that eat small fish have higher values than sharks that eat whales and are higher in the food chain.
The researchers then examined the food web plotted by the numbers on ancient teeth. The results showed interesting patterns.
Dr. “We have the same zinc isotope values in great white sharks, in the same region as Megalodon,” McCormack said. “Super interesting. They’re obviously very different in size, but that means there’s an overlap in their prey types.”
He paints a picture of the gigantic shark gliding across its shadow like a bus chasing the hapless fish, and in the background, a relatively tiny shape at the time, the great white catches the same prey for itself.
If the great white ate prey of the same species, then perhaps smaller sharks were competing with the megalodon for food. If so, they may have contributed to its eventual collapse alongside potential changes in other aspects of the ecosystem, such as climate. it’s an idea scientists swam pastDr. But there’s no geochemical evidence to support the hypothesis, McCormack said.
Researchers hope that a measurement like the zinc isotope value can help fill in the gaps as they try to piece together what ecosystems were like millions of years ago – who ate who and where. Going this far back in time is still a new idea, but perhaps with more data than any other living thing, it could help us understand what happened a long time ago, when organisms like megalodon blinked in the fossil record.
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