Illustration of a hammerhead shark of the Sphyrnidae family. (Pixabay/Baechi)
COTEKNO.COM – One of the mysterious events that nearly wiped out sharks on Earth recently came to light from a series of accidental investigations.
More than 19 million years ago, experts said that the oceans were literally teeming with sharks, roughly ten times as many as today.
However, the large marine predator almost disappeared due to a strange event. The evidence available so far still does not explain what caused the extinction.
“We studied microfossils of fish teeth and shark scales in deep-sea sediments and decided to make the numbers of fish and sharks for 85 years,” said Elizabeth Sibert of Yale University. Science Alert, Friday (4/6/2021).
When the team compared the denticle ratio of ancient sharks to the teeth of other fish buried up to 5,700 meters on the ocean floor, the experts saw clear changes in marine life that occurred around 19 million years.
Previously, sediment samples had many denticles and teeth, which naturally fell from the fish’s body and landed on the ocean floor.
Now, only a third of the samples contain evidence of shark denticles.
This unexpected drop in shark abundance was twice as large as what was found in the Cretaceous-Paleogene extinction event, which wiped out the dinosaurs.
In sediment cores from the North Pacific and South Pacific, the researchers found evidence of a sharp decline in shark abundance, estimated to be more than 90 percent.
This is a worrying discovery because it means sharks are having a hard time recovering from a sudden extinction event.
Since the 1970s, modern marine sharks have declined by about 70 percent, mainly due to overfishing.
After these ancient sharks went extinct, researchers found that tuna, seabirds and whales began to fill in the gaps and that may be one of the reasons why sharks have a hard time recovering. (Suara.com/Lintang Siltya Utami)