Great white sharks may have contributed to megalodon extinction, study says

The megalodon, a giant shark that lived over 23 million years ago and was the inspiration for the movie “Megashark” (2018), was nearly four times the size of the great white shark that crosses our oceans today.

However, the two shark species, which at some point coexisted, likely hunted some of the same prey. That competition may have been one of the reasons the 20-meter-long megalodon became extinct, a new study suggests.

To arrive at this discovery, the researchers involved in the study used a new technique. They analyzed dietary traces left in the teeth of 13 extinct species of sharks and 20 modern sharks to understand where they fit in the food chain – a place scientifically known as the trophic level.

“The megalodon is often portrayed as a massive, monstrous shark in fiction, but the reality is that we know very little about this extinct shark,” said study author Kenshu Shimada, a professor of paleontobiology at DePaul University in Chicago and researcher associate of the Sternberg Museum of Natural History, Kansas.

“Our new study shows that the dietary range of the early Pliocene white shark is very similar to that of the megalodon, indicating that our data do not contradict the competition hypothesis,” he said via email.

The researchers were able to gather this information by looking at the presence of different isotopes, or variants, of the chemical element zinc preserved in the sharks’ tooth enamel.

Zinc is essential for living beings and plays an important role in the development of bones. The balance between heavier and lighter zinc isotopes in the teeth preserves a record of the type of animal matter that sharks ate.

“Zinc isotopes can be used as ecological indicators because the rate of two different isotopes changes as you move up the food chain,” said co-author Michael Griffiths, a geochemist and professor in the department of environmental science at William Paterson University in New Jersey.

For example, if the megalodon ate great white sharks, their higher position in the food chain would have been reflected in the isotope records. But studies showed that the species had parts in common, which suggests they shared similar items.

However, the authors cautioned that they cannot claim that megalodons did not prey on great whites, given that their isotope values, particularly from a close relative of megalodon called megalodon chubutensishad lower values ​​than any vertebrate or modern fossils analyzed.

Feeding at the same trophic level does not necessarily imply direct competition between the megalodon and the great white shark for the same prey. However, at least some overlap between the food items of the two species is likely, the study found.

“Like the great whites of today, they [os megalodontes] probably fed on large fish. The smaller white sharks presumably didn’t need as much food as the megalodon, so they had the competitive advantage if they were vying for the same prey,” said Griffiths.

The research was published in the scientific journal Nature Communications on Tuesday (31).

This study represents the first time it has been proven that diet-related isotopes of zinc are preserved in shark teeth.

A similar technique, using nitrogen isotopes, studying the dietary records of other groups of animals, is well established, the study says. However, nitrogen is not well preserved in teeth enough to study animals that went extinct millions of years ago.

The technique using zinc isotopes can be applied to other extinct animals to understand their diet and ecology.