Size of Extinct Megalodon Is Off the Charts

Schematic drawing showing the distribution of maximum possible sizes of all known 70 non-planktivorous genera (groups) in the shark order Lamniformes, comprising modern (in gray) and extinct (in black; with hypothetical silhouettes) members and in comparison with an average adult human (in red) as scale. It is important to note the anomalously large size of the iconic megatooth shark, Otodus megalodon (50 feet), and the fact that the Cenozoic Era (after the age of dinosaurs, including today) saw more lamniform genera attaining larger body sizes than the Mesozoic Era (age of dinosaurs). (Image by DePaul University / Kenshu Shimada)

(CN) — Some creatures are so big they capture the public imagination. T-Rex. Triceratops. Titanosaur. And the megalodon, an iconic megatooth shark that dominated the oceans for millions of years.

Megalodon was the subject of the 2018 sci-fi thriller “The Meg,” though filmmakers took the liberty of exaggerating the size and capability of the prehistoric creature that died out 3.6 million years ago.

A new study published in the journal Historical Biology concludes that the scientifically justifiable maximum body size of megalodon was about 50 feet. While smaller than earlier estimates of the species, megalodon were significantly larger than whale sharks, the largest fish in the oceans today at 40 feet.

The study “illuminates exactly how uniquely gigantic (Otodus megalodon) was,” said lead author Kenshu Shimada, a professor of paleobiology at DePaul University in Chicago and research associate at the Sternberg Museum of Natural History in Kansas.

Shimada, who has been studying prehistoric sharks for nearly 40 years after finding a megalodon tooth in his native Japan when he was 13, also studies present-day sharks to understand the species biology.

Utilizing data he accumulated over the last two decades, Shimada and his colleagues — Martin Becker and Michael L. Griffiths, both environmental science professors at William Paterson University in New Jersey — examined specimens of all 13 living species of a shark group called lamniforms. Common lamniforms include great white sharks and sand sharks.

The trio generated a conservative mathematical model to capture the relationship between tooth size and body length, then applied the equation to all known lineages of extinct non-planktivorous lamniforms based on their front, or anterior, teeth. Because sharks are comprised primarily of cartilage instead of bone, little of their forms survive in fossils except for their teeth.

The study results were surprising because practically all other non-planktivorous sharks have a general size limit of 23 feet. Only a few plankton-eating sharks, such as the whale shark, came close to the size of megalodon.

“The significance of this new study is that it is the first collective analysis surveying the body sizes of all major lamniform shark lineages including both extinct and living forms,” Shimada said. “It demonstrates Megalodon to be uniquely gigantic relative to other non-planktivorous sharks.”

In the animal kingdom, size matters for a variety of reasons.

“For animals and especially sharks, body size affects the range of travelling distances, predation risks, energy storage capacity, and the extent of heat retention that may in turn influence their life history and behavioral strategies,” the study authors wrote.

Megalodon’s gigantism likely allowed it to thrive in oceans across the planet. But what helped them grow so much larger than other sharks?

Shimada’s study concluded that warm-bloodedness, coupled with the likely occurrence of shark embryos cannibalizing their littermates in the womb, enabled megalodon offspring to gain more weight before they were born. If accurate, the extra size increased their chances for survival.

“Lamniform sharks have represented major carnivores in oceans since the age of dinosaurs, so it is reasonable to assert that they must have played an important role in shaping the marine ecosystems we know today,” said Shimada.

So why study the fossil record? Shimada believes the more we know about ancient creatures, the better prepared we are to help current species thrive.

“The fossil record provides a window into the evolution of ecosystem dynamics, and understanding why species become extinct and how their rise and demise affect the rest of the ecosystem is critical to today’s oceans for issues like conservation of organisms, habitat preservation, and sustainable marine natural resources,” Shimada said. “Deciphering ecological variables as simple as the body size of organisms, especially carnivores like sharks in our new study, is the first step.”

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