It seems that one of the most fearsome sharks to ever roam the planet was killed off 1m years earlier than we originally thought.
It seemed fitting that an ancient creature that inspired many a science fiction film over the years could only have been made extinct by something as powerful and literally astronomical in scale as a distant supernova irradiating the planet. However, new findings due to be published to the journal PeerJ have found evidence that the megalodon shark died long before the cataclysmic event 2.6m years ago.
The team of US and UK palaeontologists examined previous data on the 15-metre-long shark and found that, in many places, there were problems regarding individual fossils in the study estimating the extinction date. So, in this new study, the team reported every fossil occurrence of O. megalodon from the densely sampled rock record of California and Baja California in Mexico in order to estimate the extinction.
It found that genuine fossils were present until the end of the early Pliocene epoch approximately 3.6m years ago, but all fossils after this time either had poor data provenance and likely came from other sites, or they showed evidence of being eroded from older deposits. After making substantive adjustments to the data and reanalysing it, the team concluded that the megalodon would have been killed off 1m years before the supernova event.
Rise of the great white
The new data also makes it unclear as to whether the proposed mass extinction event was actually one at all, as marine mammal fossils between 1m- and 2m-years-old are extraordinarily rare, resulting in a 2m-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,” said Robert Boessenecker of the University of Wisconsin, who led the team.
In attempting to put forward a possible reason for the megalodon’s extinction, the team said that competition with the newly evolved great white shark was the likely answer. This is because great whites first showed serrated teeth approximately 6m years ago in the Pacific, before spreading worldwide 2m years later.
“We propose that this short overlap was sufficient time for great white sharks to spread worldwide and outcompete O. megalodon throughout its range, driving it to extinction, rather than radiation from outer space,” Boessenecker said.