Megalodons were giants of the ocean. But without fossils of megalodon skeletons, scientists don’t know exactly how big they were. Many researchers have calculated their size by comparing megalodon teeth with great white shark teeth. Because of similarities in the sharks’ teeth and diets, scientists assume that megalodons’ bodies grew in much the same way that great whites’ do. “The two sharks are like distant cousins,” says Shimada.
In 2019, Shimada used great white shark teeth to estimate the length of the megalodon. He found that the sharks could reach at least 15 meters (50 feet)—more than twice as long as a great white!
The next year, Shimada’s team learned that megalodons were far larger than their extinct relatives. To find the lengths of these ancient sharks, Shimada looked at the sizes of living sharks that belong to the same group as the extinct sharks and megalodons (see The Meg’s Relatives, right). After the megalodon, the next-longest shark in the group was just 7 meters (23 feet) long.
In Shimada’s newest study, in 2021, he used fossilized teeth to calculate that megalodons were giants even at birth—about 2 meters (7 feet) long! In order to grow that large, babies would likely have eaten unhatched eggs inside their mother! Some modern shark babies eat their own species too, says Shimada.