A new study shows that the megalodon, a giant shark that went extinct 3.6 million years ago, was longer and thinner than previous studies suggested. This finding changes scientists' understanding of megalodon behavior, life in the ancient ocean and the reasons for shark extinction.
The megalodon or “big-toothed shark” is typically depicted as an oversized monster in popular culture, with recent examples found in the science fiction films “The Meg” (2018) and “Meg 2: The Trench” (2023). Previous studies suggest the shark likely reached a length of at least 50 feet and possibly up to 65 feet.
However, Megalodon is largely known only from its teeth and vertebrae in the fossil record, a rather incomplete data set from which to draw assumptions. For this reason, previous studies have traditionally used the modern great white shark as a model for megalodon bodies. This model led researchers to conclude that the shark was round and stocky like the great white shark.
“Our team reexamined the fossil record and found that Megalodon was slimmer and possibly even longer than we thought. Therefore, the modern mako shark could be a better model,” said UCR biologist and lead author of the paper Phillip Sternes. “It would still have been a formidable predator at the top of the ancient marine food chain, but it would have behaved differently because of this new understanding of its body.”
For the new study, published in the journal Palaeontologia Electronica, a team of 26 scientists from around the world, co-led by Sternes and DePaul University paleobiology professor Kenshu Shimada, were inspired by differences in previously estimated megalodon body lengths.
“It was a 'eureka moment' when our research team recognized the discrepancy between two previously published lengths for the same megalodon specimen,” Shimada said.
Next, the team conducted a new comparison between Megalodon's fossil vertebrae and those of its living relatives, the lamniform sharks. “We measured the entire vertebral skeleton of a living great white shark with a CT scanner and compared it to the previous reconstruction of the megalodon spine,” said Sternes.
“It was still a huge and predatory shark. “But the results clearly suggest that Megalodon was not simply a larger version of the modern great white shark.”
A revised understanding of the megalodon's body type would, in turn, impact not only scientists' understanding of the basking shark itself, but also its influence on the ecology and evolution of the marine ecosystems that shaped today's oceans.
There is no doubt that Megalodon is one of the largest sea predators to have ever existed. However, a thinner, elongated body would suggest that Megalodon also had a longer digestive canal. Sternes explained that in this case, the sharks may have had better nutrient absorption and did not need to eat as often as previously thought.
“With a better ability to digest its food, it could have gone longer without hunting.” That means less predation pressure on other marine life,” says Sternes. “If you only had to eat a whale every now and then, whale populations would remain more stable over time.”
Some shark researchers have theorized that a natural decline in prey led to the megalodons' extinction. However, Sternes has a different theory, supported in part by a revised understanding of its form.
“I think there was a combination of factors that led to the extinction, but one of them may have been the appearance of the great white shark, which may have been more agile, making it an even better predator than the megalodon,” said Sternes. “This competition for food may have been an important factor in their disappearance.”
The research team, made up of shark experts from the US, UK, Austria, France, Japan, Mexico, Brazil and Australia, believe a revised understanding of ancient sea life would have a cascading effect on the oceans that is still visible today.
“Now that we know it was a slimmer shark, we need to re-examine its lifestyle, how it actually lived and what caused its death,” said Sternes. “This study represents an important step that others can follow.”
REFERENCE
Megalodon body shape
Photo: UC RIVERSIDE BIOLOGIST AND FIRST AUTHOR OF ARTICLE PHILLIP STERNES HOLDS A MEGALODON TOOTH.