19 million years ago, 90% of sharks mysteriously died out and could no longer regain their numbers.
Experts at Yale University found that due to an unknown mass extinction that occurred 19 million years ago, the number of sharks decreased by 90%, and their biodiversity in general fell by 70%.
Sharks are a group of fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins. The most ancient representatives existed already about 450-420 million years ago. Sharks survived the fall of an asteroid that destroyed the dinosaurs, the Permian extinction, after which 95% of the species disappeared, but something destroyed 90% of their population 19 million years ago.
In order to answer this question, the authors studied ichthyolites – fossilized remains of scales and teeth from different parts of the Pacific Ocean. According to the information received, the authors have restored the dynamics of the biological diversity of sharks and other fish over the past 80 million years.
The authors note that the extinction took place in less than 100 thousand years, they cannot say more precisely. However, during this period, there were no major climatic changes, and there is an obvious gap in sedimentary rocks that hides other versions of disturbances in the environment that could lead to a decrease in the number of sharks.
The authors continue to study this topic and do not yet express their guesses about what happened.