A brand new examine printed in Science suggests that the majority sharks and shark species died off in a mass extinction occasion 19 million years in the past. It might have been probably the most devastating extinction occasion in sharks’ 450 million-year historical past, however scientists can’t clarify what went unsuitable.
Researchers Elizabeth Sibert and Leah D. Rubin discovered proof of the mass extinction occasion in historic sediment core samples taken from the South Pacific and North Pacific waters. The samples, which comprise supplies relationship again a whole lot of thousands and thousands of years, have been collected in 1983 and 1992 by the International Ocean Discovery Program. Evidently, the 1000’s of shark scales contained in these samples have been ignored till not too long ago.
Shark scales, or denticles, are a great indicator of what number of sharks have been in an space throughout a sure interval. In that regard, the North and South Pacific core samples inform an fascinating story—the Earth’s waters held a dizzying array of sharks till 19 million years in the past, when the shark inhabitants abruptly declined by 90%. Much more troubling, about 70% of shark species went extinct presently.
However researchers can’t determine why the sharks died off so all of a sudden. Ordinary suspects, similar to water temperature and carbon cycles, seem to have been secure when the extinction occasion occurred. The thriller, it appears, received’t be solved till we now have extra information.
Sadly, we don’t have loads of information from 19 million years in the past. Scientists want to gather extra core sediment samples to see if something uncommon triggered the mass extinction occasion. As famous by Elizabeth Sibert and Leah D. Rubin, researchers haven’t had the prospect to research core samples from the Atlantic ocean, so it’s doable that this mass extinction occasion occurred solely within the Pacific ocean (although that is unlikely, as oceanic adjustments are inclined to occur on a world scale).
As we proceed to review the distant previous, we’re assured to find extra mass extinction occasions. The impression that these occasions have on Earth’s historical past and the current day could also be inconceivable to know, however at the least we will strive to determine what led to them within the first place.
Supply: Science through Ars Technica