New details revealed about Megalodon's shocking size: They ate their siblings in the womb

The research suggests that these massive sharks were born more than 6 feet in length

Megalodon, the apex predator of the seas, was the largest shark to ever live, at nearly 60 feet in length. A recently published study suggests the massive shark reached its epic size because of oophagy: a kind of intrauterine cannibalism behavior.

The research, published in the scientific journal Historical Biology, suggests that these massive sharks were born more than 6 feet in length, thanks to eating undeveloped siblings while still developing during pregnancy. 

"The gigantism of O. megalodon is attributed to the evolution of regional endothermy, possibly along with the inferred live-bearing reproductive mode involving intrauterine cannibalism in the form of oophagy," researchers wrote in the study. "Yet, exactly how O. megalodon developed throughout its lifetime has remained largely in the realm of speculations."

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In-utero cannibalism is not uncommon among sharks. In November 2019, a species of shark discovered in Kansas also portrayed in-utero "cannibalistic behavior."

In September, a separate group of researchers determined the true size of the megalodon’s body, including its huge fins, based on fossils. A 52.5-foot-long megalodon likely had a head 15.3 feet long, a dorsal fin approximately 5.3 feet tall and a tail around 12.6 feet high, the scientists found.

The scientists, led by Kenshu Shimada, used a number of methods to come up with their findings, including CT scans with multiple X-rays to reconstruct fossils and get an idea of how large a megalodon was at birth.

Shimada and the other experts also determined that the massive shark grew 6.3 inches per year for the first 50 years of its life. Megalodons had a life expectancy of around 88 years and could have reached 100 years old, the experts suggested.

"As one of the largest carnivores that ever existed on Earth, the evolution and extinction of O. megalodon must have contributed to shaping the present-day marine ecosystem," the researchers added. "Hence, deciphering such growth parameters of O. megalodon is critical to understand the role large carnivores play in the context of ecology and evolution."

The megalodon may have become extinct thanks to being outmaneuvered and outdone by its smaller, more agile cousin, the great white.

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Other theories suggest the megalodon was killed off by an exploding star approximately 2.6 million years ago.

Another theory that has gotten a lot of attention in recent memory is that the megalodon simply was unable to regulate its body temperature. Cooler ocean temperatures during the Pliocene era led its preferred food, whales, to adapt, while the megalodon was unable to,

During the Pleistocene extinction event, many animals larger than 80 pounds went extinct, according to the Illinois State Museum. At roughly 50 feet in length and a weight approaching 120,000 pounds, megalodons would have been a prime candidate to be affected by the cosmic blast.

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Fox News' James Rogers contributed to this story.