A mysterious species of shark that lived 20 million years ago and was 12 feet (3.6 metres) long has managed to escape anyone’s notice – until now.
Scientists discovered fossils belonging to the extinct species of shark in California, North Carolina, Peru and Japan.
This elusive species is an ancestor of the modern day great white and mako sharks.
A group of scientists led by Professor Kenshu Shimada, a paleobiologist at DePaul University in Chicago found teeth fossils up to 1.8 inches (4.5 cm) long.
From these fossils the scientist deduced the shark lived during the early Miocene epoch about 20 million years ago.
The newly-discovered species of shark, named Megalolamna paradoxodon, belongs to a group called Lamniformes.
The scientists said it is unusual that such a large shark managed to evade our notice for so long.
‘It’s quite remarkable that such a large lamniform shark with such a global distribution had evaded recognition until now, especially because there are numerous Miocene localities where fossil shark teeth are well sampled,’ said Professor Shimada, lead author of the study.
The paper, published in the journal Historical Biology, says the species name ‘paradoxodon,’ or paradoxical teeth, comes from the fact that the shark appears to emerge suddenly in the geologic record.
‘At first glance, teeth of Megalolamna paradoxodon look like gigantic teeth of the genus Lamna, that includes the modern porbeagle and salmon sharks,’ Professor Shimada told Live Science.
‘However, the fossil teeth are too robust for Lamna — it shows a mosaic of dental features reminiscent of the genus Otodus.’
There is a yet unresolved nearly 45-million-year gap from when Megalolamna possibly split from its closest relative, Otodus.
The researchers compared the fossils with the teeth of Carcharocles megalodon, the most massive shark ever discovered.
Megalodon could grow up to 59 feet (18 metres) long, and its bite was more powerful than T-Rex’s.
M. paradoxodon and C. megalodon both belong to the extinct family of sharks known as Otodontidae, but scientists had previously placed C. megalodon in a distinct lineage.
Now Professor Shimada and his colleagues suggest M. paradoxodon and C.megalodon are actually close cousins, and that C. megalodon should be placed in another genus called Otodus.
‘Carcharocles megalodon has been the typical expression for the fossil shark,’ Professor Shimada said.
‘The idea that megalodon and its close allies should be placed in Otodus is not new, but our study is the first of its kind that logically demonstrates the taxonomic proposition’.