World's biggest shark megalodon was wiped out because it was too slow
Megalodon - the biggest shark that ever lived - was wiped out because it was too slow, according to new research. It was not as fast as believed but had a mega-appetite - explaining its gigantism, say scientists.
The huge and powerful marine monster would have been outcompeted for resources by smaller and nimbler rivals. Evidence comes from its tiny placoid scales - the first discovery of its kind.
They lacked narrowly-spaced ridges or 'keels' - characteristic of fast-swimming fish.
Close-up view of tiny placoid scales of the iconic extinct megatooth shark (DePaul Uni/Kenshu Shimada/SWNS)Lead author Professor Kenshu Shimada, of DePaul University in Chicago, said: "This led my research team to consider O. megalodon to be an 'average swimmer' with occasional bursts of faster swimming for prey capture."
Megalodon was a rather slow cruiser that used its warm-bloodedness to facilitate digestion and absorption of nutrients. The Great White is a better hunter. They chased the same meals including whales, dolphins and porpoises.
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The US team propose radically new interpretations of the lifestyle and biology of iconic Otodus megalodon.
It overturns conventional wisdom about its swimming speed. Megalodon dominated the oceans between 23 million and 3.6 million years ago.
It was three-and-a-half times bigger than the Great White shark - reaching 65ft in length and weighing more than 50 tons.
Its serrated seven-inch fangs and the odd vertebrae are all that remain. A shark's skeleton is made of cartilage - which rarely survives fossilisation.
Megalodon's sudden extinction has puzzled evolutionary experts for decades. It has been suggested it could still be alive - the premise for the 2018 Jason Statham blockbuster The Meg and the upcoming Meg 2.
Prof Shimada says that is impossible. As a warm-water species, it would not be able to survive in the cold waters of the deep - the only chance of going unnoticed.
Megalodon's scales were identified entombed within rock pieces surrounding a previously described tooth set from Japan.
Prof Shimada said: "Our big scientific findings come from 'tiny evidence' as small as grains of sand."
The creature's biology was previously based on its gigantic teeth and vertebrae. It was traditionally assumed to be energetic - just like the makos and Great White sharks of today.
The study also leads to a paradox. Megalodon expended a high level of metabolic heat resulting from its warm-bloodedness - without being an active swimmer.
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Prof Shimada said: "It suddenly made perfect sense. Otodus megalodon must have swallowed large pieces of food. So it's quite possible the fossil shark achieved the gigantism to invest its endothermic metabolism to promote visceral food processing."
The findings are in Historical Biology.
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