Megalodon babies were 6-foot-long uterine cannibals, study suggests

Scans of a subset of its several hundred vertebrae – some the size of a grapefruit – showed the shark had died at the age of 46. The researchers estimated that the mega’s life expectancy was around 88 to 100 years, implying that their specimen had been roughly “middle-aged,” Dr Shimada said. They also back-calculated the size of the shark during its early years and found that it could be over six and a half feet long when it was born.

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

To grow to such a staggering size, the booming megas may have nibbled at each other while they were still in the womb, Dr Shimada said. Most sharks hatch from eggs inside their mother’s body and then are born alive young. But puppies of some species don’t like roommates: once hatched, they will begin to devour unhatched siblings, which will help them grow stronger before they are born.

“It’s this large, high-calorie, nutritious meal that can help these embryos grow bigger and faster,” said Allison Bronson, who studies the evolution of fish at Humboldt State University in Arcata, in California, but did not participate in the study. .

With so much weight in tow, mini-megos might have emerged ready to take on potential predators, or at least eclipse quite a few of them. A ravenous appetite, paired with warm blood, could have helped them catch a lot of prey, allowing juvenile terrors to thrive even more.

Mr Cooper said the study provided crucial data on a poorly understood animal. But he noted that some of the calculations used were based on data collected in the 1990s, when researchers relied more on great white sharks to estimate aspects of the megalodon’s anatomy. Drawing too close a comparison between the two animals, he said, can lead to “underestimates in certain specific body dimensions.”

It is also unclear just how representative this individual megalodon was for its species, Dr Bronson said. “There are a lot of variations in fish,” she says. “Even fish of the same age, of the same species, can grow at really different rates and reach really different sizes.”

Researchers cannot know how difficult carrying and giving birth to a puppy over 6 feet tall could have been for megalomothers. But “proportionately, while this baby is really big, so is the adult,” Cooper said. At full size, some megalodons could have covered almost the length of a bowling alley – plenty of room to house even an embryo the size of a basketball player.