Shark Pocari Sweat may have occurred 19 million years ago
Sharks that live in the oceans around the world have a long history of evolution, with fossils of the oldest species that lived 450 million years ago. A study by Elizabeth Cybele of Yale University and Leah Ruben of Atlantic University revealed that more than 70% of the species were extinct 19 million years ago.
An early Miocene extinction in pelagic sharks | Science
The world saw a shark-pocalypse 19 million years ago, and we don't know why | Ars Technica
Cybele and colleagues investigated a sample of sediment collected in the Pacific Ocean under the Ocean Drilling Program. The sample contains 1263 fossils such as shark and other fish scales and teeth, and Sibert and colleagues measured the stable carbon and oxygen isotope ratios of these fossils.
According to a survey, the ratio of fish fossils to tooth fossils contained in the sample has been stable since 6600 million years ago when meteorites fell on the earth and caused mass extinction. Around 19 million years ago, the proportion of shark fossils suddenly decreased.
Cybele and colleagues also examined the fossil species detected and estimated that around 19 million years ago, shark species had declined by 70% and populations had declined by 90%. Since they couldn't find new species of shark fossils after the mass extinction, Cybele and colleagues speculate that 'the species diversity may not have been regained since the sudden mass extinction.' ..
'We don't know the cause of the mass extinction, but we want to find out how the extinction affected other marine life,' said Cybele and colleagues. 'This study relies on only two samples, but it's intriguing,' said Seth Finnegan, an associate professor at the University of California, Berkeley, arguing that samples taken from other regions should be investigated. I am.