The recent discovery left researchers dumbfounded, unable to explain the immense loss or reason for the death of one of the ocean’s most powerful predators.
“We stumbled upon this thing completely by accident because what we saw was that everything was pretty stable until about 20 million years ago, when sharks declined in abundance by over 90%,” Sibert, an oceanographer and paleontologist at Yale University, told CNN. “We found that sharks were doing amazingly well on the high seas until that exact moment when they were all but extinct. We had no idea because no one had ever looked.”
“We don’t really, really know anything,” Sibert said. “This particular interval in Earth’s history is not so well preserved in the deep-sea sediments that we are examining. It is difficult to find suitable places for further study.”
Sibert and his team have few theories.
Since sharks are intimately linked to the environment in which they live, it is likely that there has been intense environmental change that has wiped out millions of species. It is unlikely that the loss can be attributed to another predator, unless it does not have existing fossils.
“It’s possible that something big happened, but whatever it was, it was really fast,” Sibert said. “The earth system could have corrected it, but these big predators, these sharks that lived in the open ocean, must have been very sensitive to this rapid environmental change. But that’s still only a guess.”
Researchers don’t know how long it took to eradicate sharks. It could have happened in a single day, or maybe 50 years, or even 100,000 years, according to Sibert.
Since sharks lived so deep in the ocean and far from land, and since the deep sea does not preserve bodies in a way that can be lifted and displayed on land, scientists in the samples have discovered organisms that ‘they had never seen before.
While the fossils found confirmed they were sharks, researchers have no way of knowing what the sharks looked like.
“Like most research efforts, this first article asks more questions than it can answer, and we plan to investigate the extent of the data denticles (V-shaped scales) offered across a diverse set of lenses, from hydrodynamics to ecology, ”said Leah Rubin, co-author of the study.
“The current state of decline in shark populations is certainly a cause for concern,” she said, “and this article helps put those declines in the context of shark populations over the past 40 million years. This background is a vital first step in understanding the repercussions of dramatic declines in these major marine predators in modern times. ”
The discovery left researchers with many unanswered questions: Did this phenomenon impact other sharks in other parts of the ocean at the same time? Did it impact other creatures living in the ocean or on land?
More importantly, what exactly happened?
“We hope that our study will spark the interest of the rest of the scientific community to dig into this time interval,” said Sibert. “Something really big must have happened because it had an impact on this truly amazing group of organisms that exist and have frankly survived major global change over the past 400 million years.”