Earth scientists from Yale University and College of the Atlantic recently made the discovery, saying it happened during a period in history where there were 10 times the amount of sharks in the ocean than today. "We happened upon this extinction almost by accident," Elizabeth Sibert with Yale University said in a news release. "What we found, though, was this sudden drop-off in shark abundance around 19 million years ago, and we knew we had to investigate further.""I study microfossil fish teeth and shark scales in deep-sea sediments, and we decided to generate an 85-million-year-long record of fish and shark abundance, just to get a sense of what the normal variability of that population looked like in the long term," Sibert continued.REL.