Dire Wolves...

 ...did really exist, outside of D&D and Game of Thrones. The giant predators, up to six feet long, evolved to eat megafauna.

The general assumption has always been that they were, well, wolves that grew in size as their prey did.

Not so!

Dire wolves were pretty dire, but they were not, in fact...wolves.

They were wild dogs, split off from the gray wolf ancestry 5.7 millions ago, that then evolved to, well, look like giant wolves.

They're going to be moved from genus Canis, where wolves and dogs live, to their own genus. And this may also explain why they didn't survive.

Canis is known for its adaptability at many levels. Wolves and coyotes can easily change their ways to survive. And the genetic plasticity that gives us everything from huskies to chihuahuas to spaniels to pugs...

...may not have been present in this other lineage of dogs. And they appear to have been unable to cheerfully interbreed with other dogs the way all true canids can.

We'll probably still keep calling them dire wolves, though, the way we call Chrysocyon brachyurus "maned wolves" even though they also are not, ya know...wolves.

So, here's a thought, scientists: Have you compared dire wolf DNA to Chrysocyon brachyurus, another highly-specialized dog that doesn't count as a true canid...and also apparently native to the New World.

Just a random thought.