Megalodons might have been even larger than we first thought, growing up to 80 feet (24.3 meters) long — 15 feet (4.5 m) longer than previous predictions, according to a new study.
These massive sharks may also have been more slender than originally believed, the researchers said.
"Previous estimates using teeth to predict its size had the shark reaching about 18-20 meters total length (59-65 feet)," study co-author Phillip Sternes, an educator at SeaWorld San Diego, told Live Science in an email.
Megalodon ruled the seas of ancient Earth between around 20 million and 3.6 million years ago. No complete megalodon (Otodus megalodon) skeletons have ever been found, so our knowledge of these behemoths comes from fossils of their vertebrae scales and teeth. The largest megalodon fossil ever found is a 36-foot-long (11 m) section of its spine, which would have been located in the trunk of its body.
In the new study, published Sunday (March 9) in the journal Palaeontologia Electronica, researchers examined megalodon fossils and compared them with more than 150 living and extinct shark species to build a better picture of just how big this giant shark was.
The researchers compared the proportions of the megalodon's trunk with the trunks of 145 modern and 20 extinct shark species.
Related: What did 'the meg' look like? We have no idea
Assuming that the megalodon was roughly proportional to the majority of other shark species, and extrapolating from the 36-foot (11 m) trunk section, the researchers estimated that this individual may have had a 6-foot-long (1.8 m) head and 12-foot-long (3.6 m) tail, giving it a total length of 54 feet (16.4 meters).
However, the largest megalodon vertebra ever found measured up to 9 inches (23 centimeters) in diameter — 3 inches (7.6 cm) bigger than the largest vertebra from the 54-foot shark. Scaling up from this larger vertebra, and based on the previous proportions, the megalodon it belonged to may have measured 80 feet long.
The researchers also found that the megalodon may have given birth to live young measuring 12 to 13 feet (3.6 to 3.9 m) long.
Megalodon shape
The researchers behind the new study also investigated the megaladon's shape.
Megalodon tooth fossils are serrated and resemble the teeth of modern-day great white sharks (Carcharodon carcharias), which previously led researchers to assume that megalodon looked similar to great whites.
"Previous studies simply assumed that megalodon must have looked like a gigantic version of the modern great white shark without any evidence," study lead author Kenshu Shimada, a paleobiology professor at DePaul University in Chicago, told Live Science in an email.
However, according to the new study, the megalodon may have actually looked more slender and streamlined.
Based on the revised maximum body size, as well as hydrodynamic models of how large creatures like whale sharks (Rhincodon typus), basking sharks (Cetorhinus maximus) and whales move through the water, the researchers conclude that the megalodon wasn't stocky like a great white and instead was more similar to a lemon shark (Negaprion brevirostris).
However, until researchers find a larger section of a megalodon's body in the fossil record, we won't truly know how large they could get, or what shape their bodies may have been.
Jack Cooper, a megalodon researcher at Swansea University in the U.K. who was not involved in this new study, isn't convinced by the study authors' argument that megalodon looked more like lemon sharks than great whites.
"The hydrodynamic methods they use to try to rule out these other body forms are based primarily on whales, which have totally different skeletons and modes of swimming to sharks (i.e., vertical vs horizontal tail movements)," Cooper said. "As such, while the proposed body plan is possible, it should be treated as a working hypothesis and previous reconstructions can't yet be definitively ruled out."
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