Bulky or slender? Megalodon study reignites debate over extinct shark.

Visitors examine the massive jaw of the extinct megalodon displayed at a museum. (Rick Loomis/Getty Images)
8 min

The extinct shark megalodon is often imagined as a beefy, supersize great white, with a gaping maw of pointy teeth capping off a powerful body that spanned 50 feet from nose to tail. Now, a team of more than two dozen scientists argues that the megalodon has been misunderstood, and may have been slimmer and longer than previous estimates.

The new study, published in the journal Palaeontologia Electronica, is the latest chapter in an ongoing scientific dispute about what this apex marine predator really looked like and what its role was in ancient ocean ecosystems.

Otodus megalodon has been extinct for some 3.6 million years, but many nonexperts have a mental picture of this prehistoric super-shark. Reproductions of its massive jaw provide a backdrop for family photo ops at aquariums across the country. The megalodon spawned its own Hollywood franchise with the 2018 horror flick “The Meg.” And a 52-foot, some 2,000-pound model dangles menacingly over the cafeteria at the National Museum of Natural History.

The catch is that these are feats of scientifically informed imagination — and the basic question of what megalodon looked like is a thorny topic among experts.

What scientists know for sure is that megalodon had giant teeth, some as big as an adult human hand. They’ve dug up segments of its fossilized backbone. And they recently analyzed some of its tiny scales. But its cartilage skeleton doesn’t fossilize well, so many scientists have leaned on analogies to a living macropredator with similar-shaped teeth: the great white shark.

“We’re trying to speculate on something based on the very incomplete pool of evidence,” said Michael Gottfried, a vertebrate paleontologist at Michigan State University who was not involved in the new study.

Multiple outside experts said the study — which posits an elongated and slender megalodon more similar to a mako shark than a great white — won’t settle the matter. Even if the megalodon is longer than previously proposed, they point out, it could still have had a robust, bulky body. But the back and forth highlights the level of fascination that scientists and the general public have with this creature.

Pieces of a backbone in Belgium

Much of what is known about the megalodon’s body stems from a collection of 141 pieces of its backbone discovered in the 1860s in Belgium.

In the 1990s, Gottfried measured pieces of that backbone. In modern-day great whites, there’s a mathematical relationship between the width of their vertebrae and their total length. When Gottfried applied that to the megalodon vertebrae, he calculated that the Belgian specimen must have been 30 feet long.

In a previous job, at the Calvert Marine Museum in Maryland, he constructed a reproduction skeleton of a megalodon, scaling up from a white shark and making adjustments to the proportions.

Then, in 2022, a different team of scientists returned to the Belgian specimen to create a 3D model. Drawing heavily on analogies to great white sharks, but also considering other modern sharks, they reported that the megalodon specimen was 52 feet long, weighing some 67 tons — a “transoceanic superpredator” that was probably able to cruise faster than any living shark, with a stomach big enough to ingest an orca.

Other shark experts had grumbles about the findings. The new study is in many ways a direct response: A team of more than two dozen scientists came together to point out flaws and make a counterargument. Their interpretation of the same specimen suggests that the megalodon was more slender — and possibly even longer than previously thought.

“The slender body would indicate that Megalodon may not have been a powerful swimmer as much as the modern great white shark is, and this is consistent with the interpretation that Megalodon may have been a slow-cruising shark,” Kenshu Shimada, the senior author of the new paper and a paleobiology professor at DePaul University in Chicago, said in an email.

Shimada said the new interpretation supports a recent study from his lab that examined fossilized placoid scales, the type of tiny, pointed scales unique to sharks and rays. That research suggested that the megalodon “was generally a slow cruiser with occasional ‘burst swimming’ for capturing prey,” he said.

But both teams have pointed critiques of each others’ studies, a normal — if sometimes uncomfortable — part of how science moves forward.

Jack Cooper, a graduate student and shark paleontologist at Swansea University in Wales who led the study that is under attack, said that his team’s work has been criticized because of its overreliance on the great white shark as an analog to megalodon. But the new interpretation originates from an analysis that also relies on comparison to a great white.

He also disagreed that a thin backbone would necessarily be too narrow to support a bulky animal, pointing out that the extinct shark cretoxyrhina also had a slender vertebral column but a bulky body form.

Outside experts said both papers still use speculation to arrive at their different interpretations.

“At the end of the day, I don’t think it brings us that much closer to knowing what megalodon really looks like,” said Robert Boessenecker, a coastal paleontologist at the nonprofit Charleston Center for Paleontology who was not involved in the new study.

Dana Ehret, curator of natural history at the New Jersey State Museum, said that it was good to see biologists who study modern shark biology join the discussion of ancient sharks, and, for him, the interesting thing is that both papers suggest that the megalodon was probably longer than scientists once thought.

“Some of the biggest sharks today are whale sharks, basking sharks. They max out at 35 to 40 feet,” Ehret said. “Think of a shark another 20 feet longer than the biggest shark today. To me, that is really mind-boggling.”

Celebrity megapredators

It’s not unusual for paleontologists to disagree about ancient animal bodies — sometimes with a ferocious intensity. Gottfried recalled witnessing some scientists get into a heated disagreement over the angle of the thigh bone when assembling a triceratops specimen.

John Hutchinson, a professor of evolutionary biomechanics at the Royal Veterinary College at the University of London, is part of the team that put forward the controversial 3D model of the megalodon. He said that the stakes are always high in science, but particularly when working on species that attract both public and scientific fascination.

“The more celebrity an extinct animal has, and the rarer it is, the more competitive or heated the disagreements can be,” Hutchinson said. “I know this all too well. I worked on T. rex.”

Hutchinson said that, early in his career, people used 2D illustrations of fossilized skeletons and shrink-wrapped skin around them, making them quite skinny. Based on these models, people believed Tyrannosaurus rex was around 11,000 pounds. But now, using various methods, scientists mostly agree that an adult T. rex would have been somewhere around 17,000 pounds.

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The question matters not only because people want to put a face to these megapredators, but also because form can help explain function, which in turn has consequences for our understanding of ancient and modern ecosystems.

“This was one of the largest marine carnivores to ever live, and it was clearly a major component in the marine ecosystem,” said Phillip Sternes, a graduate student and shark paleontologist at the University of California at Riverside and lead author of the study.

The latest disagreements may provide little clarity on what the megalodon looked like — but the scientific competition between research groups has spurred more research, and pushed the field beyond papers that simply describe the discovery of new specimens to research delving into ancient ecology.

For instance, the megalodon is estimated to have gone extinct some 3.6 million years ago, perhaps because of competition for prey with the great white shark. And previous work suggested that when the megalodon vanished, the absence of a fierce ocean predator allowed for the rise of modern filter-feeding whales.

“The last five to 10 years or so, the study of megalodon has really changed considerably — from sort of stamp collecting to actual hypothesis-driven paleobiological study,” Boessenecker said.