Controversial study claims megalodon didn't look like a 50-foot giant great white shark

By Melissa Hobson

 

Scientists say they have discovered a discrepancy in previous research and suggest megalodons may have been longer and more slender than previously believed — but not everyone is convinced.

Megalodon size and shape has been revised by researchers in a new study, but the findings have been met with criticism. (Image credit: Sayouna/Shutterstock)

Megalodon, the biggest shark to have ever lived, may not have looked like an uber great white shark as is generally assumed — but instead may have been longer and thinner, scientists have revealed. 

By reanalyzing the incomplete spine of a fossilized megalodon (Otodus megalodon) held at the Royal Belgian Institute of Natural Sciences (IRSNB) in Brussels, the team found discrepancies in previous reconstructions, which suggested these supersized shark had a body length of around 52 feet (16 meters) and a shape resembling great white sharks.

"The previously published reconstruction of Megalodon skeleton and body shape looked very awkward," co-author Kenshu Shimada, a paleobiologist at DePaul University in Chicago, told Live Science in an email. 

The team of 26 shark experts revealed their findings in a new study, published Jan. 21 in the journal Palaeontologia Electronica.

Great white sharks (Carcharodon carcharias) are often used as a model to inform estimates about megalodon's size and what it might have looked like. This is because shark skeletons are made largely of cartilage — which is less likely to be preserved as fossils than bone — so scientists have only found fossilized teeth and vertebrae from megalodon. As a close relative and apex predator with similar diet and traits, great whites are thought to be an appropriate model.

Related: What did 'the meg' look like? We have no idea

In the new study, the researchers examined CT scans of a juvenile great white’s vertebral skeleton and then compared it to the vertebra of the megalodon specimen. Their findings showed differences in the growth of the centrum — the solid, central part of the vertebrae. In living Lamniform sharks (the order that megalodon and great whites belong to), centrum growth relates to girth, the team wrote. The megalodon's vertebral column was found to be much thinner than the great white's, which they interpret as meaning the meg was far more slender than a great white.

The previous analysis suggested a vertebrae length of 36.4 feet (11.1 m), but the new findings indicate this would have been the minimum length. The researchers say megalodon was likely longer and slimmer, so it might not look like the great white shark model after all. "We still don't know the exact shape of its head, fins, or tail," Shimada said.

Instead, megalodon might have resembled something closer to a mako shark (Isurus oxyrinchus), co-lead author Phillip Sternes, a biologist at University of California Riverside, said in a statement. 

So, how big could megalodon have been? The researchers don't want to give a definitive length without solid evidence, but this new information suggests it could have "easily" reached 50 feet (15 m) long and may even have reached 66 feet (20 m) "or possibly slightly more," Shimada said.

"The reality is that we need the discovery of at least one complete Megalodon skeleton to be more confident about its true size as well as its body form," Shimada said. 

Despite questioning the findings from the previous study, the research team still believe it was important and say it was significant in helping the team reach its new conclusions. It's "an excellent example of how science advances," Shimada said.

The authors of the previous study are not convinced by the new findings, however. Lead author Jack Cooper, a researcher at Swansea University in the U.K., along with his colleagues Catalina Pimiento, also at Swansea University, and John Hutchinson, at the Royal Veterinary College, say the new study is more of an alternative hypothesis that suffers from "circular logic" — where an argument assumes its conclusion is correct, and uses the conclusion to support the argument

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"Moreover, they don't actually provide a new length estimation in their work," they told Live Science in an email. The new study, they added, ignores the fact that the previous analysis considered multiple living examples of sharks alive today, and that one of their models also showed an elongated body when based on great white sharks alone. 

"Importantly, the 'elongated body' interpretation is based on a single observation, a comparison with a single analogue, and lacks any statistical tests to support its hypothesis," they said. "More critically, several aspects of the study are impossible for future researchers to verify or replicate as the authors do not provide the raw data."

Was Megalodon Slimmer Than Previously Thought?

A new study has spurred scientists to debate the shape of prehistory’s biggest shark

Riley Black
Science Correspondent

SMITHSONIAN

January 21, 2024 

A museum curator gives a sense of scale to the reconstructed jaws of the fossil shark Otodus megalodon. 

Rick Meyer / Contributor via Getty Images


In the more than 400 million years that sharks have been swimming through Earth’s seas, none has been larger than Otodus megalodon. The great megatoothed shark reached more than 50 feet in length and prowled oceans the world over between 2.6 million and 23 million years ago. Despite the shark’s success and its fame as a massive apex predator worthy of multiple B-movies, paleontologists are still investigating what the giant shark actually looked like. And a new proposal suggests that O. megalodon was more slender than previously thought.

The latest study, published Sunday in Palaeontologia Electronica, draws from a portion of an O. megalodon backbone to suggest that the shark had a proportionally longer body than that of the modern great white shark. But some outside experts are doubtful about the new restoration.

Paleontologists have been investigating and revising the proportions of O. megalodon for decades. Experts principally work from teeth and vertebrae from the shark to estimate its size and proportions, which is common for prehistoric sharks, as their cartilaginous skeletons often decayed before fossilization. The shark’s spotty fossil record makes it challenging to get an exact idea of what the great fish looked like. “No complete skeleton of O. megalodon has been discovered yet, and that is why deciphering its body size and form have been so challenging,” says DePaul University paleontologist and study co-author Kenshu Shimada.

Just because a complete O. megalodon skeleton is unlikely to have been fossilized, however, doesn’t mean paleontologists are totally in the dark about what the shark looked like. O. megalodon belonged to a group of sharks called lamniformes, which includes species like the great white, salmon shark, porbeagle and others. The modern sharks share some key attributes with O. megalodon, such as body temperatures elevated above the surrounding seawater and preferences for fat-rich prey to help fuel their active lifestyles. O. megalodon probably resembled its modern relatives, but the details are still being discussed by experts.

The new study by Shimada and colleagues is the latest attempt to outline what O. megalodon might have looked like and is largely a response to a 2022 study from a different research team. Both studies are based on the same O. megalodon vertebrae, but they reached different conclusions.

In the latest study, the researchers scaled up a great white’s proportions so that its vertebrae would have the same diameter as the O. megalodon vertebrae. In this case, an O. megalodon with great white proportions would be about 30 feet long. However, the actual length of the partial backbone is about 36 feet—significantly longer than the great white model suggests. To resolve the discrepancy, the researchers propose that O. megalodon had a more elongated form than a great white of the same size would.

“Our new study suggests that we need to think outside the box when it comes to inferring the biology of O. megalodon,” Shimada says.

The new study suggests that the megatooth shark had an elongated body form compared to today’s great white. 

DePaul University / Kenshu Shimada


But the researchers behind the 2022 research are not convinced by the new hypothesis. “While alternative hypotheses should be and are welcomed in science, this particular proposal suffers from a circular logic,” says paleontologist Jack Cooper of Swansea University in Wales, who was not involved in the new study.

The new study says that the great white shark is an inappropriate analogue for O. megalodon, Cooper notes, but the new research also uses the great white shark for its comparisons of body form to the exclusion of other sharks. The 2022 study, by comparison, considered other lamniform sharks in addition to the great white and created a three-dimensional model. The 2022 study also produced an elongated O. megalodon model as one of its possible outcomes, as well, but researchers ruled it out based on data from a broader array of lamniform sharks.

Lacking a complete O. megalodon skeleton, such disagreements may seem difficult to resolve. “However,” Cooper says, “sharks have generally remained geometrically similar throughout their long evolutionary history, which means living sharks can be informative in reconstructing extinct ones.” Even when the shark’s record is mostly teeth and isolated vertebrae, scientists can still generate a rough idea of the megatooth’s shape based on physiology, what it likely fed on and other details gleaned from the fossil record.

University of California, Riverside, biologist and study co-author Phillip Sternes holds an O. megalodon tooth. 

Douglas Long / California Academy of Sciences

Working out the shark’s form is critical to understanding how the megatoothed shark lived during its long tenure in Earth’s seas. “The body plan of megalodon is a key part of understanding its wider ecology, such as how fast it swam and what it needed to eat,” Cooper says. A longer shark would swim differently, for example, or have organs like the liver and spiral intestine related to the shark’s feeding and digestion. O. megalodon thrived for about 20 million years before vanishing, even as its preferred prey survived. Understanding the shark’s form can help experts uncover the carnivore’s evolution and extinction.

For the moment, however, Cooper and colleagues are not swayed by the new reconstruction. All researchers are agreed that O. megalodon was not simply a supersized great white, but what kind of shape the enormous shark took as it slid through ancient waters is only just beginning to come into focus.



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Riley Black is a freelance science writer specializing in evolution, paleontology and natural history who blogs regularly for Scientific American.