Giant shark ''megalodon'' went extinct earlier than thought

Washington

Megalodon—a giant predatory shark that has inspired numerous books and blockbuster movies—likely went extinct at least one million years earlier than previously thought, a study has found.

Earlier research, which used a worldwide sample of fossils, suggested that the 50-foot-long, giant shark Otodus megalodon went extinct 2.6 million years ago. 

Another recent study attempted to link this extinction, and that of other marine species, with a supernova known to have occurred at about this time.

Researchers from University of Wisconsin Oshkosh in the US noted that in many places there were problems with the data regarding individual fossils in the study estimating the extinction date.

The research, published in the Journal of Life and Environmental Sciences, showed every fossil occurrence of O megalodon from the densely sampled rock record of California and Baja California (Mexico) in order to estimate the extinction.

Researchers found that genuine fossil occurrences were present until the end of the early Pliocene epoch, 3.6 million years ago.

All later fossils either had poor data provenance and likely came from other fossil sites or showed evidence of being eroded from older deposits.

Until 3.6 million years ago, O megalodon had a continuous fossil record on the West Coast.

"We used the same worldwide dataset as earlier researchers but thoroughly vetted every fossil occurrence, and found that most of the dates had several problems-fossils with dates too young or imprecise, fossils that have been misidentified, or old dates that have since been refined by improvements in geology; and we now know the specimens are much younger," said Sarah Boessenecker of the University of Leicester in the UK.

"After making extensive adjustments to this worldwide sample and statistically re-analysing the data, we found that the extinction of O megalodon must have happened at least one million years earlier than previously determined," said Boessenecker.

This is a substantial adjustment as it means that O megalodon likely went extinct long before a suite of strange seals, walruses, sea cows, porpoises, dolphins and whales all disappeared sometime about 1-2.5 million years ago.

"The extinction of O megalodon was previously thought to be related to this marine mass extinction-but in reality, we now know the two are not immediately related," Boessenecker said.

It also is further unclear if this proposed mass extinction is actually an extinction, as marine mammal fossils between 1 and 2 million years old are extraordinarily rare-giving a two-million- year-long period of "wiggle room".

"Rather, it is possible that there was a period of faunal turnover (many species becoming extinct and many new species appearing) rather than a true immediate and catastrophic extinction caused by an astronomical cataclysm like a supernova," Boessenecker said.

The researchers speculate that competition with the newly evolved modern great white shark (Carcharodon carcharias) is a more likely reason for megalodon's extinction.

Great whites first show up with serrated teeth about 6 million years ago and only in the Pacific; by 4 million years ago, they are finally found worldwide. PTI