The giant shark is back. Five years after The Meg, in which action star Jason Statham battled a huge prehistoric shark, the follow-up Meg 2: The Trench is upon us. Once again, Statham will be victimised by a supposedly extinct gigantic shark, in increasingly outlandish ways: the trailer has him fending off its huge upper jaw with his foot, and leaping over the animal using a water scooter. The trailer also has a scene involving a plate-glass window that relies on audiences being too young to have seen Deep Blue Sea.
It comes as something of a shock to learn that this clearly deeply silly film is directed by Ben Wheatley, the acclaimed director of leftfield horrors and black comedies like A Field in England and Free Fire. Evidently, he is hoping to make the same jump to the mainstream that Greta Gerwig achieved with Barbie.
Regardless of what audiences think of the film, however, the creature it portrays was once very real indeed. Megalodon sharks terrorised the oceans for up to 20 million years, before dying out about 3.5 million years ago, too long ago for humanity to encounter them. They were the largest sharks ever to exist and one of the largest marine predators. But just how big they were and how they got that way has only become clear in the last few years. New research is even providing insights into how these creatures may have lived, hunted and fed.
Megalodon sharks have been known to science since the 1840s, thanks to their huge triangular teeth, which are often fossilised. The name “megalodon” means “big tooth” in Ancient Greek. The species was originally dubbed Carcharodon megalodon, placing it in the same genus as the modern great white shark, but nowadays it is classed as Otodus megalodon.
They weren’t kidding about the big teeth: some specimens are 16.8cm (6.6in) long. For comparison, great white shark teeth top out around 7.5cm (3in). Clearly, megalodon was a big shark, but how big?
If we had a complete skeleton this would be a fairly easy question, but we don’t. Sharks are cartilaginous fish, meaning their skeletons are made of soft cartilage instead of hard bone, and cartilage doesn’t fossilise well. As a result, the megalodon fossil record mostly consists of teeth, plus a few vertebrae as those are partially mineralised. “We really don’t have a great handle on what the shark actually looked like,” says Sora Kim, an ecogeochemist at the University of California, Merced, who studies the chemistry of megalodon teeth.
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This means the true size and shape of megalodon is uncertain. Instead, palaeontologists estimate it. They have done so by measuring the sizes of megalodon teeth, comparing them to the teeth of other sharks whose body sizes are known, and scaling those bodies up. This is inherently uncertain, because larger animals aren’t simply magnified versions of smaller ones.
Hence there have been disagreements. Many studies have suggested megalodon could grow to 18m (59ft) or even 20m (66ft). However, in a 2019 study, palaeobiologist Kenshu Shimada at DePaul University in Chicago argued that those estimates were flawed. He argued that the upper front teeth were the best metric, and they yielded a maximum length of 15.3m (50.2ft).