Zoom in on the invisible world of the atom

Were sharks, those ruthless survivors of global extinction waves, gone almost 19 million years ago?

Hear the famous jawsThe topic is already almost in your head when you see pictures of a white shark. However, even without the magic of Hollywood, the world’s largest predatory fish is perhaps the most famous of the nearly 450 species of sharks that glide across the world’s oceans.

And then we do not count all the species that died out long ago, their number is estimated at several thousand. With fantastic creatures like Megalodon, the largest shark ever, a masterpiece of many museum collections and the star of his own movie series (Meg).

For hundreds of millions of years, it has been difficult to imagine the sharks of our oceans without them. They’ve been here long before our appearance and have survived so many global extinctions that scientists have spent years figuring out what makes them so difficult. These explanations: the fact that they can handle temperature fluctuations well, and the fact that they love everything they can sink their teeth into (the proverb sometimes), so that they can eat enough during a global catastrophe.

Great white shark, like the one in the movie JawsBuild Getty Images

near extinction

However, recent research erodes that untouchable picture. in the magazine Science Two palaeobiologists write about 19 million years ago, when sharks nearly disappeared. They discovered near extinction by looking at the so-called teeth, small-sized teeth on the outer surface of sharks help, among other things, to glide more efficiently through the water. Something that inspired swimwear maker Speedo to create the famous “shark” suit, which is considered a “technological dope” due to its effectiveness in formal swimming competitions – but regardless.

The teeth They regularly circulate to the ocean floor, where they are preserved as fossils. About 19 million years ago, the number of these in the soil decreased abruptly. The authors concluded that about 70 percent of all shark species switched by that time must have disappeared.

And strange? During that period, as far as we know, nothing special happened to Earth’s climate or environment. So the researchers discovered something completely new. At least, unless something else is going on. After all, it is also possible that a file teeth themselves – in composition, for example – so that they are not well preserved.

“Modern sharks began to diversify about two to five million years after the extinction wave, but they represent only a small sliver of what sharks once were,” the researchers wrote in their paper. In other words, had it not been for what happened 19 million years ago, jaws Probably more persecuted now.

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