How great whites may have contributed to the extinction of the biggest shark, megalodon

It had 276 teeth and grew longer than a bus. So why did megalodon die out around 4 million years ago? (Supplied: CSIRO)

With a mouth you could easily step through and serrated teeth as big as your hand, megalodon was the biggest shark the world's seen.

But around 4 million years ago, this formidable apex predator died out. What was behind its downfall?