Did Great White Sharks Wipe Out the Giant Megalodon?
Why did the mega-shark megalodon die out? It could have been its highly active metabolism, new research suggests.
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O grande tubarão-branco (Carcharodon carcharias) pode ter varrido o gigante megalodon (Otodus megalodon).
Milhões de anos antes de os seres humanos surgirem, um tipo de tubarão que cresceu até 18 metros de comprimento rondou os oceanos. Com base no registro fóssil, os cientistas suspeitam que O. megalodon tenha morrido há cerca de 2,6 milhões de anos, na mesma época em que muitas outras espécies marinhas foram extintas. (Pesquisadores até recentemente sugeriram que a morte em massa pode ter sido o resultado de uma supernova próxima.)[These Bizarre Sea Monsters Once Ruled the Ocean]
But scientists may have miscalculated megalodon's time of death by about 1 million years.
For a paper published today (Feb. 13) in the journal PeerJ,
researchers re-examined the fossil record of megalodons in California
and Baja California, Mexico, where many examples of the huge fish have
been found.
There's clear evidence that up until about 3.6 million years ago,
megalodons were alive in the ocean. But after that, things get dodgy.
Fossils dated to between 2.6 million and 3.6 million years ago tended to
have issues. Many of the fossils seemed to have shifted within the
surrounding rock in ways that complicate the dating methods scientists
use.
But if megalodons died out 3.6 million years ago, they weren't part of that mass marine extinction. So, what killed them?
The researchers in the new study suggested that the huge sharks were outcompeted by a smaller, savvier predator.
Great whites arrived in the oceans about 4 million years ago, just 400,000 years before megalodon's revised death date.
"We propose that this short overlap (3.6 to 4 million years ago) was
sufficient time for great white sharks to spread worldwide and
outcompete O. megalodon throughout its range, driving it to
extinction," College of Charleston paleontologist Robert Boessenecker,
an author of the study, said in a statement.
Boessenecker also suggested that the whole idea of a sudden marine
die-off 2.6 million years ago may be an artifact of gaps in the fossil
record, rather than the result of some "cataclysm" like a supernova.
As for the great whites, if they know what killed the giant megalodon, they aren't telling.
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