Even before appearing as fictional pets in the television series Game of Thrones, dire wolves had long captured imaginations. Weighing around 150 pounds, the creatures were larger than the heaviest of today’s gray wolves. They roamed throughout large swaths of the Americas and preyed on now extinct megafauna, such as Ice Age horses and ground sloths.

But much about them remains unknown. Where did they come from? How similar were they to today’s gray wolves? And why did they die out around 13,000 years ago, after surviving for hundreds of millennia?

In the first study of its kind, researchers have analyzed several full genomes for these creatures, revealing a few surprises. Rather than sharing close genetic ties with the gray