Giant shark reached 15m because of 'cannibalism in womb'

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A new study published in the journal Historical Biology found that the prehistoric and extinct megalodon shark could have grown much bigger than previously estimated, if it ate its siblings in the womb like some modern shark species do.

1. Megalodon swimming, chasing shark
2. Catching up with shark, killing it
3. Size comparison: previous and new estimates
4. Shark pup hatches, eats sibling eggs inside womb
5. Shark pup swims from womb to womb to eat sibling eggs
6. Megalodon pup eats siblings, grows, birthed, grows even larger

VOICEOVER (in English):
"Scientists have calculated that the prehistoric and extinct megalodon shark could have grown much bigger than previously estimated."

"According to a study led by paleobiologist Kenshu Shimada of DePaul University in Chicago, some megalodon sharks could have grown to as long as 15 meters."

"That's 50 feet, or twice the length of a double-decker bus. At this length the ocean monster would have weighed close to a 100 tons."

"Previous estimates of the megalodon's length put it at about 33 feet, or 10 meters, based on fossilised teeth, but the new study says that estimate was too low."

"Shimada's research team said the new estimate of up to 15 meters was made after a more accurate equation was applied, based on the size sharks can grow to today if they develop in favorable water temperatures."

"The findings of the DePaul University research team have been published in the journal Historical Biology."

"The study found that this great size could have been achieved if the megalodon did what many sharks do today — eat their brothers and sisters while they're still in their mother's womb."

"Most species of modern sharks have wombs containing many eggs with shark embryos in each egg. In many species, when the first shark pup hatches inside the mother, it proceeds to eat the rest of the eggs — a behavior called intrauterine cannibalism."

"In fact, when researchers used ultrasound to inspect the dual wombs of a pregnant shark, they found that a shark pup would sometimes swim from one of its mother's wombs to the other, in order to eat the unhatched eggs in the other womb."

"Shimada says megalodon could reach a massive size of up to 15 meters, thanks to adaptations like live births, early hatching and cannibalistic feeding on other eggs in the womb."

"Over 3.6 million years ago, this combination of adaptations would have allowed the giant predator to grow to unparalleled sizes in comparison to other shark species."

"By eating their siblings, the megalodon would have grown much larger while still in the womb. Coming out larger would give them a greater chance of surviving, and a larger adult body size. If they developed in favourable water temperatures, these factors would have combined to allow them to grow to the gigantic lengths the research team claims they could reach."

SOURCES: Smithsonian,, IGN, IBTimes