CNN)About 19 million years ago, roughly 90% of the world's open-ocean sharks died off, and scientists don't know why.
The recent discovery left researchers stunned, unable to explain the immense loss or the reason behind the deaths of one of the ocean's most powerful predators.
It began when scientist Elizabeth Sibert and her team were trying to learn more about the fish and shark abundance over the last 80 million years, according to a study released on June 3. "We stumbled into this thing completely by accident because what we saw was everything was pretty stable until about 20 million years when sharks dropped off in abundance by over 90%," Sibert, an oceanographer and paleontologist at Yale University, told CNN. "We found that sharks were doing incredibly well in the open ocean until this one moment in time when they virtually disappeared. We had no idea because no one had ever looked."