About 19 million years ago, about 90% of the world’s open-sea sharks died, and scientists don’t know why.
Recent discoveries have surprised researchers and failed to explain the enormous losses and reasons behind the death of one of the most powerful predators in the ocean.
It started when scientist Elizabeth Cybele and her team were trying to learn more about the abundance of fish and sharks over the last 80 million years. The study was announced June 3rd.
“I happened to run into this problem because everything was pretty stable until about 20 million years, when sharks fell more than 90% in large numbers,” Sibert, an oceanographer and paleontologist at Yale University, told CNN. Told. “We found that until this moment when the shark virtually disappeared, we were doing incredibly well in the open ocean. We didn’t know because no one had seen it. did.”
At that time, the number of sharks swimming in the oceans around the world was ten times higher than it is today. The loss was also twice the number of sharks that “cleaned up three-quarters of the flora and fauna species on Earth” during the Cretaceous-Paleogene mass extinction 66 million years ago. Research news release.
“We really, really don’t know anything,” Sibert said. “This particular interval in Earth’s history is not very well preserved in the deep-sea sediments we see. It is difficult to find a suitable place to do additional research.”
Sibert and her team have several theories.
Since sharks are so closely related to the environment in which they live, there may have been drastic environmental changes that wiped out millions of species. Unless there is an existing fossil record, the loss is unlikely to be due to another predator.
“Something big could have happened, but whatever it was, it was very quick,” Sibert said. “The Earth’s system was able to fix that, but these big predators, these sharks that lived in the open ocean, must have been very sensitive to this rapid environmental change. Is still just a hypothesis. “
Researchers don’t know how long it took to eradicate sharks. According to Sibert, it can happen in a day, 50 years, or even 100,000 years.
Sample scientists have never seen sharks because they lived deep in the ocean, far from land, and because they did not save their bodies to lift and expose them to land in the deep sea. I found the discovered creature.
The fossils found have confirmed that it is a shark, but researchers have no way of knowing what the shark will look like.
“Like most research efforts, this first treatise offers an unanswerable number of questions. Data provided through a variety of lens sets, from fluid mechanics to ecology. Denticles (V) We plan to investigate the width of the “shaped scales”, “says Leah Rubin. , Co-author of the study.
“The current state of shark population decline is certainly a source of concern,” she said. “And this treatise helps explain these declines in the context of shark populations over the last 40 million years. How this context translates into the dramatic decline in these top marine predators in modern times. It’s an important first step in understanding how the impact will continue. “
This discovery left many unanswered questions for researchers. Did this phenomonen affect other sharks in other parts of the ocean at the same time? Did it affect other creatures living in the sea or land?
Most importantly, what exactly happened?
“We hope our research will stimulate interest in other scientific communities to delve into this time interval,” Sibert said. “It must have happened because it has affected this truly incredible group of creatures that have frankly survived major global changes over the last 400 million years.”
Scientists say 90% of the world’s open-ocean sharks died off in mystery extinction event 19 million years ago Source link Scientists say 90% of the world’s open-ocean sharks died off in mystery extinction event 19 million years ago