Extinct dire wolves split off from other wolves nearly six million years ago and were only a distant relative of today’s wolves, new research suggests.

The animals – which have gained recent fame through the TV show Game Of Thrones – were common across North America until around 13,000 years ago, after which they went extinct.

The study shows that dire wolves were so different from other canine species like coyotes and grey wolves that they were not able to breed with each other.

Previous analyses, based on morphology alone, had led scientists to believe they were closely related to grey wolves.

The team sequenced the ancient DNA of five dire wolf sub-fossils from Wyoming, Idaho, Ohio, and Tennessee, dating to more than 50,000 years ago.

The analyses showed that dire wolves and grey wolves were in fact very distant cousins.

This is the first time ancient DNA has been taken from dire wolves revealing a complex history of these ice age predators, researchers say.

The study, published in the Nature journal, analysed the genomes of dire wolves alongside those of many different wolf-like canid species.

It found that unlike many canid species who apparently migrated repeatedly between North America and Eurasia over time, dire wolves evolved solely in North America for millions of years.

Scientists found no evidence that dire wolves interbred with coyotes and grey wolves, despite overlapping with them in North America for at least 10,000 years.

The researchers suggest their deep evolutionary differences meant that they were likely ill-equipped to adapt to changing conditions at the end of the ice age.

Lead author, Dr Angela Perri from Durham University’s archaeology department, said: “Dire wolves have always been an iconic representation of the last ice age in the Americas and now a pop culture icon thanks to Game Of Thrones, but what we know about their evolutionary history has been limited to what we can see from the size and shape of their bones and teeth.

“With this first ancient DNA analysis of dire wolves we have revealed that the history of dire wolves we thought we knew – particularly a close relationship to grey wolves – is actually much more complicated than we previously thought.

“Instead of being closely related to other North American canids, like grey wolves and coyotes, we found that dire wolves represent a branch that split off from others millions of years ago, representing the last of a now extinct lineage.”

Co-lead author, Dr Alice Mouton, from the University of California Los Angeles, added: “We have found the dire wolf is not closely related to the grey wolf.

“Further we show that the dire wolf never interbred with the grey wolf. In contrast, grey wolves, African wolves, dogs, coyotes and jackals can and do interbreed.

“Dire wolves likely diverged from grey wolves more than five million years ago, which was a great surprise that this divergence occurred so early.

“This finding highlights how special and unique the dire wolf was.”

The dire wolf is a prehistoric carnivore from Pleistocene America which became extinct around 13,000 years ago.

Known scientifically as Canis dirus, meaning ’fearsome dog’, they preyed on large mammals like bison.

The researchers suggest the dire wolves’ stark evolutionary divergence from grey wolves places them in an entirely different genus – Aenocyon dirus (terrible wolf)- as first proposed by palaeontologist John Campbell Merriam more 100 years ago.

The research was led by Durham University in the UK alongside scientists at the University of Oxford, Ludwig Maximilian University in Germany, the University of Adelaide in Australia and the University of California Los Angeles in the US.