Lemmysuchus obtusidens lived around 164 million years ago and was a member of an extinct group of marine crocodile relatives called teleosaurs.
Ian Fraser Kilmister, better known as Lemmy, was the founder, bassist and lead singer of English rock band Motorhead. He died aged 70 in 2015.
"With a metre-long skull and a total length of 5.8 metres, it would have been one of the biggest coastal predators of its time," said Michela Johnson, from University of Edinburgh in the UK, who helped to untangle the identity of Lemmysuchus - which translates as Lemmy's Crocodile.
However, it was incorrectly categorised with the remains of other sea crocodiles found in the same location.
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In a study published in the Zoological Journal of the Linnean Society, an international team of scientists took a fresh look at the fossil skeleton and gave it a new classification and scientific name.
Lemmysuchus lived in shallow sea waters around the coast of land that would become modern-day Europe.
Its broad snout and large blunt teeth evolved for crushing shelled prey such as turtles - in contrast to its close relatives that had longer snouts and thinner teeth for catching fish.
"Although Lemmy passed away at the end of 2015, we would like to think that he would have raised a glass to Lemmysuchus, one of the nastiest sea creatures to have ever inhabited the Earth," said Steel.
The exact relationship between Lemmysuchus and its close relatives had been misunderstood as scientists had previously wrongly assigned some other fossil finds to the same species.
The current research team performed a careful anatomical comparison on the all bones and referred them to the main type specimen in the Museum.