They ruled the seas for millions of years as one of the most fearsome predators on Earth.

But new estimates suggest that giant megalodon sharks were even larger than previously thought: They were as much as 19.8 meters in length instead of 15.2 meters 50 feet.

Growing to the size of a cricket field, it was the most massive shark species that ever lived and was three times the size of today’s largest great white sharks.

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Huge: New estimates suggest megalodon sharks were even larger than previously thought — reaching up to 65 feet in length instead of 50 feet. They grew to be the size of a cricket field and three times the size of today’s largest great whites (comparison is shown)

New equations for calculating the size of a megalodon based on the width of shark teeth (shown) rather than height were developed after a math exercise for high school students went wrong

### HOW BIG WAS THE MEGALODON?

The largest megalodons would likely have had a head about 15 feet long, a 5 foot 4 in dorsal fin and a 12.6 foot long tail, research suggests

With a dorsal fin the size of a full-grown human and a total length of up to 65 feet, the megalodon shaded the largest shark alive today, the great white, which grows to between 15 feet and 20 feet in length at most.

The oceanic behemoth lived from about 15 million to three million years ago and has been featured in Hollywood movies, including the Jason Statham blockbuster, Meg.

In previous studies, academics estimated that it had a body length of up to 52 ft (16 meters).

A person of this size would probably have had a head about 15 feet long, a 5 foot 4 inch dorsal fin, and a 12.6 foot long tail.

This means that an average-sized adult human can stand on the shark’s back and look just over the top of the dorsal fin.

However, a new study suggests that the calculations used to estimate a megalodon’s size were wrong.

Instead of about 50 feet, researchers now say the giant extinct shark may have reached 65 feet in length — the size of a cricket field.

Victor Perez, assistant curator of paleontology at the Calvert Marine Museum in Maryland, was lead author.

The revised estimate came about when a school lesson went wrong, leading to the creation of new equations based on the width of a megalodon’s teeth rather than the height.

Victor Perez, lead author of the new study, was a doctoral student at the Florida Museum of Natural History when he challenged a group of California students to a math exercise.

It used 3D-printed replicas of fossil teeth of a real megalodon — which dominated the oceans from about 15 to 3.6 million years ago — and a series of commonly used equations based on tooth height to estimate the shark’s size.

But when the students’ calculations ranged from about 40 ft (12.1 meters) to 148 ft (45 meters) for the same shark, Perez was left stunned.

He said, ‘I was walking around, checking if you used the wrong equation? Have you forgotten to convert your units?

‘But it soon became clear that it wasn’t the students who made the mistake. It was just that the equations weren’t as accurate as we predicted.’

Although scientists have used the equations widely since their publication in 2002, the classroom exercise found that they lead to different estimates of a shark’s size depending on which tooth is measured.

“I think a lot of people would have seen that study and blindly accepted the comparisons,” said Perez, now assistant curator of paleontology at the Calvert Marine Museum in Maryland.

Scientists have been trying to calculate the size of megalodon sharks for more than a century, but the only known remains of the extinct species are fossilized teeth and a few vertebrae.

As with other sharks, the rest of the skeleton was made up of lightweight cartilage that disintegrated shortly after death.

Tooth enamel for the megalodon — whose name means “big tooth” — “preserves very well,” Perez said, and because each tooth loses thousands of teeth during its lifetime, there are plenty of fossils to study.

The most widely accepted methods for estimating the length of megalodons have used great white sharks as a modern equation, based on the relationship between tooth size and total body length.

Terrifying: Megalodons (pictured) dominated the oceans from about 15 to 3.6 million years ago

Researchers developed a new set of equations based on tooth width, then analyzed fossil teeth from 11 individual sharks, including megalodon (pictured) and modern great white sharks

But the problem with that is that, as in humans, the size and shape of shark teeth vary depending on where they are in the mouth, so a researcher must first correctly identify the fossilized tooth’s former position in a megalodon’s jaw.

Since most are found as standalone fossils, this can be tricky.

Perez was able to get around this problem when fossil collector Gordon Hubbell donated a nearly complete set of teeth from the same megalodon to the Florida Museum in 2015, removing the guesswork.

Museum researchers CT scanned the teeth before Perez teamed up with the Academy of the Holy Names school in Tampa, Florida, and Delta Charter High School in Aptos, California to create a new lesson plan for the subject.

But when the California students submitted their calculations, they ranged by more than 100 feet — the farther a tooth is from the front of the jaw, the larger its estimated size.

Perez was stunned, so wrote about the results of the lesson in a fossil community newsletter. He then got an email from Teddy Badaut, a professional paleontologist in France, who suggested measuring tooth width instead of height.

Previous research had suggested that tooth width was limited by the size of a shark’s jaw, which would be proportional to its body size.

Calculations: Researchers were able to estimate the size of a megalodon based on its tooth width

Perez developed a new set of equations based on tooth width, before he and his fellow researchers analyzed sets of fossil teeth from 11 individual sharks, representing five species, including megalodon, its closest relatives and modern great white sharks.

By measuring the combined width of each tooth in a row, they developed a model for how wide an individual tooth was in relation to the jaw for a given species.

Now when a paleontologist digs up a lone megalodon tooth, they can compare its width to the average obtained in the study and estimate how big the shark was.

However, Perez cautioned that because individual sharks vary in size, the team’s methods still have a margin of error of about three meters when applied to the largest species.

It’s also unclear exactly how wide a megalodon’s jaw was and difficult to guess based on teeth alone — some shark species have gaps between each tooth, while others overlap.

“While this may expand our understanding, we haven’t really solved the question of how big megalodon was,” Perez said.

“There’s more that can be done, but that would probably require a complete skeleton to be found at this point.”

The study is published in the journal Palaeontologia Electronica.

### WHAT IS THE MEGALODON?

The megalodon, meaning large tooth, lived between 15.9 and 2.6 million years ago.

C. megalodon is considered one of the largest and most powerful predators in vertebrate history, and fossil remains suggest it could grow up to 19 meters in length.

The monster is thought to have looked like a beefier version of today’s dreaded great white shark and weighed up to 100 tons.

Megalodon is known for fossilized vertebrae and teeth, which are triangular and have a diagonal length of almost 20 cm.

It took famed fossil hunter Vito “Megalodon” Bertucci nearly 20 years to reconstruct the jaw of a megalodon — the largest ever assembled — measuring 11 feet long and nearly 9 feet long.

The Megalodon’s colossal mouth is said to have produced a but force of 10.8 to 18.2 tons.

The ancient shark has been described as a super predator, as it could swim at high speeds and kill a wide variety of prey, such as sea turtles and whales, quickly in its strong jaws.

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