megalodon (Otodus megalodon), one of the largest sharks ever to survive, mysteriously disappeared from fossils about 3.6 million years ago. Scientists now suspect that the massive predator may have been driven to extinction by rival marine species: great white sharks.
Previous research has suggested that the decline of megalodon may coincide with the appearance of great white sharks (Carcharodon carcharias), who probably hunted the same prey as their older cousin Jeremy McCormack, a geoscientist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and lead author of a new study on these prehistoric rivals, told Live Science in an email. In support of this explanation for the relatively sudden disappearance of the megalodon were traces of bites on the bones of other marine animals; these traits are made of both large white and megalodon, suggesting that the two species may have competed for similar food resources.
But these bite marks provided only a picture of isolated interactions between predators and prey, McCormack said. To find out if great white sharks really do not exist from the hunger megalodon, you will need a more complete study of the diets of both species.
That’s why McCormack and his colleagues looked for clues in the animals’ teeth; they did not look at the size or shape of the tooth, but rather the amount of zinc present in each tooth.
Connected: What caused the mega toothache of this huge megalodon?
“Zinc is essential for organisms because it plays an important role in a wide range of biological processes,” McCormack said. Most importantly, zinc is incorporated into teeth as they grow. When the predator hunts, it ingests minerals and nutrients from its prey. One of these minerals is zinc, which is available in two isotopes (variations of the same element with different numbers of neutrons). One zinc isotope is heavier and the other is lighter. Other researchers who have previously analyzed animal teeth have found that the ratios of heavier to lighter zinc isotopes in animal teeth can reveal the animal’s position in the food chain. If the teeth contain more of the lighter isotope and less of the heavier isotope, the animal is closer to the top of the food chain in its ecosystem. But if the teeth contain more than the heavier isotope, the animal is likely to feed from below. These ratios of zinc allow scientists to determine the trophic position of an ancient animal with great accuracy.
McCormack and colleagues studied the teeth of 20 modern fish species, including sharks from wild and aquarium populations. The researchers then compared the ratios of zinc in the teeth of live fish to those in the teeth of the ancient great white and extinct megalodon.
Great white sharks evolved about 4 million years ago, overlapping with megalodon for approximately 400,000 years, Live Science reported earlier. Initially, the megalodon and the great whites occupied separate niches and did not compete with each other. But scientists have found that the ratio of zinc in shark fossil teeth documents a change in this relationship that causes them to directly collide with the fins. In the early Pliocene, or about 5.3 million years ago, some populations of large whites began to shift their position up the food chain to become top predators, invading megalodon territory. This would mean that the two species were then forced to share resources, with the more efficient hunter expelling the less efficient from existence.
In addition to competition with the great whites, the “disappearance of Otodus megalodon “These factors could include climate change and the collapse of available food resources in general, in addition to being outnumbered by large whites.”
This study was published May 31 in the journal Natural communications (opens in a new tab). (opens in a new tab)
Originally published in Live Science.