The largest shark discovered to date — the monstrous Otodus megalodon — may have been a sleek, long-bodied leviathan.

A fresh look at the extinct predator’s fossilized remains suggests its body was many meters longer and possibly more slender than previous reconstructions, researchers report January 22 in Palaeontologia Electronica. The findings may offer better insights into the biology and lifestyle of megalodon, including how fast it swam or what it ate (SN: 6/27/23). 

Reconstructing what ancient, extinct animals looked like when they were alive is challenging, even when complete fossilized remains are available. But reconstructing megalodon is much harder. Like all sharks, the giant had a cartilaginous skeleton that preserves poorly relative to bone. It is mostly known from teeth and many meters of fossilized, cartilaginous vertebrae, with the rest of the skeleton remaining a mystery.

Traditionally, modern great white sharks (Carcharodon carcharias) have been used as a model for megalodon’s body shape. That’s because great whites are the largest predatory sharks alive today and great whites and megalodons are categorized in somewhat closely related families.

A 2022 reconstruction that extrapolated from great whites caught the attention of Kenshu Shimada, a paleobiologist at DePaul University in Chicago, and his colleagues. That study based its reconstruction on the cartilaginous vertebral column of purported megalodon remains housed in a Belgian museum. Adding together all the vertebrae end-to-end revealed a body length of over 11 meters. But Shimada and his colleagues noticed that older work on that same specimen from the 1990s had calculated the entire animal’s length as about 9 meters. That work was based on the diameters of the vertebrae and how those scale with size in great white sharks, which tops out at around 6 meters long. But the 2022 study still assumed megalodon was more or less great white-shaped, Shimada and his colleagues argue.

In their reassessment of the Belgian megalodon specimen’s vertebral column and the 2022 reconstruction, Shimada and his team question relying on the shape of great white sharks to build our view of megalodon. Megalodon’s vertebral column is relatively thin compared with the sturdier vertebrae that support the beefy brawn of great whites, makos and other modern relatives, the team notes. The researchers offer a new interpretation: Because such a small vertebral column would make more sense in a longer, leaner body shape, megalodon may have been built more like a bus than a van. Overall, it may have been an even bigger predator than researchers thought, Shimada says. 

This study was “a major learning moment for both myself and many other scientists in that we need to take a broader perspective when reconstructing extinct animals, especially megalodon,” says coauthor Phillip Sternes, an organismal biologist at the University of California, Riverside.

A slender body may mean that megalodon wasn’t as powerful a swimmer as great whites are. This matches recent research from Shimada and his colleagues on the shape of a megalodon scale that suggested the shark was a slow cruiser capable of short bursts of speed. This shift in body shape may hint at how it ate or how much it ate, says paleontologist Dana Ehret of the New Jersey State Museum in Trenton, who was not involved in either work.

“When working with extinct species, especially ones that don’t have any close living relatives today, we do our best by estimating what they may have looked like or how they behaved but it is never exact,” he says.

The new study takes an interesting approach, says vertebrate paleontologist Michael Gottfried, but the researchers still rely on great white sharks as a model in some ways, like on patterns of the size of vertebrae in different parts of the shark’s body. Gottfried and his colleagues were the researchers who measured and reconstructed the Belgian specimen as roughly 9 meters long in the 1990s. He says he isn’t sure how accurately the vertebrae can be added up to a total length, because many of the vertebrae are incomplete or fragmentary. 

“Ultimately, we are still speculating on body form and many other aspects of megalodon,” says Gottfried, of Michigan State University in East Lansing. Additional fossil material from the head and fins would be crucial for understanding how the giant shark looked.

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