Dire wolves, which died out 13,000 years ago, ended a separate lineage from wolves.

The ancient, extinct dire wolf may have been among the lonest of the wolves - so genetically distinct from its closest wolf relative that it could no longer interbreed, forcing it into an evolutionary dead end when it died out 13,000 years ago.

That's the finding based on a new study, the in-depth analysis of DNA retrieved from ancient dire wolf bones from across North America. Once dire wolves (Canis dirus) diverged from grey wolves millions of years ago, they seem to have never mingled since.

In fact, so different is their genetic lineage from other canids that the research team proposes that dire wolves be placed in another genus completely - that they be reclassified as Aenocyon dirus, as was first proposed all the way back in 1918.

"Dire wolves are sometimes portrayed as mythical creatures - giant wolves prowling bleak frozen landscapes - but reality turns out to be even more interesting," said palaeobiologist Kieren Mitchell of the University of Adelaide in Australia.

"Despite anatomical similarities between grey wolves and dire wolves - suggesting that they could perhaps be related in the same way as modern humans and Neanderthals - our genetic results show these two species of wolf are much more like distant cousins, like humans and chimpanzees."

Dire wolf remains can be found in the fossil record from 250,000 to around 13,000 years ago, and seem to have dominated the carnivore scene during the last Ice Age in what is now North America. Read the free article.