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The Mighty Megalodon

Scientists study fossilized teeth to size up a giant shark!

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As you read, think about how fossils form and what information they provide to scientists.

DePaul University/Jeff Carrion

Skye Basak is up to her elbows in mud. After hours of digging, she pries loose a stone, revealing a shark tooth that’s 16 centimeters (6 inches) long. A tooth that big could be from just one shark: a giant prehistoric one called a megalodon!

Basak is a fossil hunter who runs a company called Palmetto Fossil Excursions in Summerville, South Carolina. She often shares the fossils she finds with a local museum for research. Megalodon teeth are some of Basak’s favorite fossils to dig up. They can be three times as large as those of great white sharks! 

Kenshu Shimada is a scientist at DePaul University in Chicago who studies fossils to learn about prehistoric life. In recent years, he has used megalodon teeth, like the ones Basak finds, to better understand this massive fish!

Skye Basak is up to her elbows in mud. She’s been digging for hours. She lifts a stone and sees a shark tooth. It’s 16 centimeters (6 inches) long. That’s really big for a tooth! It could only come from one shark: a giant that lived long ago. It was called a megalodon!

Basak is a fossil hunter. She runs a company called Palmetto Fossil Excursions. It’s in Summerville, South Carolina. Basak often shares the fossils she finds with a local museum. Megalodon teeth are some of Basak’s favorite fossils to find. They can be three times as large as great white shark teeth! 

Kenshu Shimada is a scientist who works at DePaul University. It’s in Chicago. He studies fossils to learn about ancient life. He’s uses megalodon teeth, like the ones Basak finds, to learn more about this huge fish! 

Back in Time

Megalodons lived around the globe between 15 million and 3.6 million years ago. They spent time in tropical waters along coastlines and used sawlike teeth to feed on large fish, seals, and whales. Scientists have found whale fossils with big bite marks that likely came from the giant sharks!

Scientists think the megalodon’s jaws had more than 200 teeth lined up in rows, explains Shimada. As the sharks fed on other animals, these teeth often fell out. This happens to today’s sharks too.  

When a megalodon lost a tooth, it sank to the ocean floor and was covered by sediments. Over millions of years, the sediments turned to rock. At the same time, minerals entered the tiny spaces in the tooth and hardened, forming a fossil. Then wind and water gradually wore away the rock in a process called weathering (see How Shark Teeth Became Fossils, below).

Megalodon teeth have been found on every continent except Antarctica. But fossils of other shark body parts are rare. Teeth are made out of hard, bone-like material. But shark skeletons are made of cartilage, the same tissue the tip of your nose and the outer parts of your ears are made from. Cartilage is much softer than teeth. It usually breaks down before it can become a fossil.

Megalodons once swam the world’s oceans. They lived between 15 million and 3.6 million years ago. They spent time in tropical waters along coastlines. Megalodons used their sawlike teeth to eat large fish, seals, and whales. Scientists have found whale fossils with big bite marks. The bit marks likely came from megalodons!

Scientists think the megalodon had more than 200 teeth, says Shimada. They lined up in rows. The teeth often fell out as the sharks fed. This happens to today’s sharks too.  

The lost tooth would sink to the ocean floor. There, it was covered by sediments. The sand and dirt slowly turned to rock. This took millions of years. Minerals filled tiny spaces in the tooth and hardened to form a fossil. Then wind and water slowly wore away the surrounding rock. This is called weathering (see How Shark Teeth Became Fossils, below).

Megalodon teeth have been found on every continent except Antarctica. But fossils of other shark body parts are rare. Teeth are hard. They’re made of a bone-like material. But shark skeletons are made of cartilage. The same tissue forms the tip of your nose and your ears. Cartilage is much softer than teeth. It usually breaks down before it can become a fossil.

Just How Big?

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. 

Megalodons were giants of the ocean. But there are no fossils of their skeletons. So scientists don’t know exactly how big they were. Many scientists have estimated their size. They did this by comparing their teeth to those of great white sharks. The teeth are very similar. So scientists think megalodons grew in the same way great whites’ do. “The two sharks are like distant cousins,” says Shimada.

Shimada measured great white shark teeth in 2019. He used them to figure out the megalodon’s length. He found that it could reach at least 15 meters (50 feet). That’s more than twice as long as a great white! 

Shimada’s team found something else the next year. Megalodons were even larger than related extinct sharks. Shimada figured this out using measurements of living sharks. They belonged to the same group as the ancient 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. 

Shimada did a new study in 2021. He used fossil teeth to learn megalodon’s size at birth. The babies were huge—about 2 meters (7 feet) long! The sharks must have eaten unhatched eggs inside their mother. That’s the only way they could have grown that large! Some modern shark babies eat their own species too, says Shimada. 

Palmetto Fossil Excursions

Fossil hunter Skye Basak carefully digs for shark teeth in South Carolina.

More to Discover

The more scientists learn about megalodons, the better they can understand what the planet was like millions of years ago. “We want to know why the megalodon became so large and why it became extinct,” Shimada says. 

To find these answers, scientists like Shimada will continue to study fossils to look for clues about the past. Meanwhile, researchers and fossil hunters will keep digging for more megalodon teeth. For Skye Basak, each discovery is exciting! “When you find a fossil, you’re the first person on Earth to lay eyes on it or touch it,” she says.

Scientists want to find out more about megalodons. That way they can better learn what the planet was like millions of years ago. “We want to know why the megalodon became so large and why it became extinct,” Shimada says. 

Scientists like Shimada will study fossils to find these answers. Fossil hunters will also keep digging for megalodon teeth. Each discovery is exciting for Skye Basak! “When you find a fossil, you’re the first person on Earth to lay eyes on it or touch it,” she says.

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