The Trilobites column of the New York Times has a story about sharks... big sharks. Otodus megalodon, commonly referred to as Megalodon, is regarded as one of the largest predators that ever lived. Estimates of its size extrapolated from teeth put it at between 46 and 67 feet (14 - 20.3 meters). A new paper in the journal Nature Communications looks to address what pushed O. megalodon to extinction, was it climate change or competition for food resources.
Twenty million years ago, a predator with a mouth like a subway door and teeth the size of your palm roamed the seas. The megalodon, the largest shark ever to live on Earth, could grow more than 50 feet long, and it was the scourge of the ocean for millions of years. Then it disappeared. The megalodon was no more.
Exactly what happened to push this beast of a shark to extinction is a topic of much debate among scientists. Now a paper published Tuesday in the journal Nature Communications suggests that great white sharks, which coexisted with the megalodon, preyed upon the same kinds of animals the much larger shark ate. This evidence helps to support the theory that competition with the great white, a predator that is still going strong today, might have been one factor that took the megalodon out of the picture. It also highlights the idea that a predator doesn’t have to be the biggest to eventually dominate an ecosystem.
Reconstructing the food chains of long-ago oceans is a difficult task, said Jeremy McCormack, a geoscientist at the Max Planck Institute for Evolutionary Anthropology in Germany and an author of the new paper. You can’t watch extinct animals feeding or set up a camera to spy on how they lived.
But there are other methods. One option for deducing what an animal ate is examining the molecules that make up its body. Zinc isotope levels in the teeth of present-day mammals correlate with where they fall in the food chain, many other studies have found: The higher up the food chain an animal is, the lower the zinc isotope values they show. Because teeth fossilize well, the team wondered whether the same would hold true if they looked at teeth from millions of years ago.
