Experts at Yale University found that due to an unknown mass extinction that occurred
Sharks are a group of fish characterized bythe presence of a cartilaginous skeleton, from 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 asteroid strike that wiped out the dinosaurs, the Permian extinction event that wiped out 95% of the species, but something wiped out 90% of their population 19 million years ago.
To answer this question, the authorsstudied ichthyolites - fossilized remains of scales and teeth from different parts of the Pacific Ocean. Based on the information received, the authors reconstructed the dynamics of the biological diversity of sharks and other fish over the past 80 million years.
The authors note that extinctionhappened in less than 100 thousand years, they cannot say more precisely. However, there were no major climate changes during this period, and there is a clear gap in the sediment that obscures other theories about environmental disturbances that may have led to the decline in shark numbers.
The authors continue to study this topic and have not yet expressed their guesses about what happened.
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