The study indicates that young megalodons were cannibals 6 feet tall

Scans of a subset of nearly hundreds of its vertebrae – some the size of a grapefruit – showed that the shark had died at the age of 46. Researchers estimated the average life expectancy of a mig to be between 88 to 100 years, meaning that their sample was roughly the same, Dr Shimada said: “Middle aged.” They also retrospectively calculated the size of the shark during its early years, and found that it may have been over six and a half feet long when it was born.

“He’s a really big kid,” said Mr. Cooper, who was not involved in the study.

Dr Shimada said that to reach this amazing size, the booming little mega might have eaten each other while in the womb. Most sharks hatch from the eggs inside their mothers’ bodies, and are then born when they are young. But puppies are of some species Don’t take kindly to roommates: Once they hatch, they will start devouring their siblings who have not hatched, which helps them to reinforce before they are born.

“It’s this great, calorie-rich, nutritious meal that can help those embryos grow faster and faster,” said Alison Bronson, who studies fish evolution at Humboldt State University in Arcata, California, but was not involved in the study.

With such heavy heft, small megas may have appeared ready to conquer with potential predators, or at least dwarf a large number of them in size. The voracious appetite, coupled with warm blood, may help them catch a lot of prey, allowing the horror of juveniles to build up even more.

Mr Cooper said the study provided important data on a poorly understood animal. But he noted that some of the calculations it used were based on data gathered in the 1990s, when researchers relied more on great white sharks to estimate aspects of megalodon anatomy. He said comparing the two animals too closely could lead to “an underestimation of some specific body dimensions”.

Dr Bronson said it’s also hard to tell how representative this single megalodon is of its kind. She said, “There are a lot of differences in fish.” “Even fish of the same age, the same species, can grow at really different rates and reach really different sizes.”

Researchers can’t tell how difficult conception and delivery of a six-foot-plus pup would be for huge moms. “In proportion, while this child is really big, so is the adult,” said Mr. Cooper. At maximum size, some megalodons may have spanned nearly the length of a bowling alley – there’s plenty of room to house even a basketball-sized fetus.