(CNN) An extinct species of wolf, which served as inspiration for a mythical creature in the popular television show "Game of Thrones," had little in common with the gray wolves that roam North America today, new research has found.

Known as Canis dirus, meaning "fearsome dog," it had been thought that dire wolves were simply a beefier version of the gray wolf.

However, a new study in the journal Silvatics has found that this ancient species possessed large powerful canines that could have completely surprised researchers. It also belonged to one of two types of "territorial species," meaning it was active in the wild and could have been known and targeted by human hunters.

The ancient predator had a wide variety of behaviors, which resemble very unusual wolves of today. These include a "hotter wolf" that could sprint as fast as 25 miles an hour, long-range hunting and "active predators" that would try to hunt its target without being seen -- even in winter when temperatures can plummet to as low as zero Fahrenheit.

While researchers don't even yet have accurate estimates of the animal's size and weight, it was likely significantly larger than the average gray wolf and likely weighed close to 350 pounds.

"One of the weird things about dire wolves was that it seems like they could fit inside larger, more typical wolf categories," said study co-author Amy Olson, a paleontologist at Vanderbilt University. "They're impressive animals in some ways, but we don't know whether they were really really large on their own, or if it's some composition effect."

It could take a great deal of large prey in a single year to compete with the large jaws of such animals. Image courtesy of the USDA

The research team used the skulls of hundreds of modern subjects to piece together what would have been a highly specialized predator, previous studies showed. Even so, for their study on this specimen, much of possible big prey were excluded.

Tasty bones

They had a large deep-set muzzle with large lips that might have sedated and excited the predatory wolves; streamlined transitional dentaries where teeth could store and squelch prey; and lower couldines with scaly lips and nostril-like openings for smelling unusual smells such as cat urine or horse-blood.

Some adults would have had very long, thick white hair on the back of their heads.

Like grey wolves today, the old creature had muscular, aplite cusps under its skulls that needed to be flicked to flip the animal to latch on. Unlike some predatory wolves today, it had no sharp teeth.

Its large ears would have supported and protected it, and male dire wolves' grey, longish sheep-like dress would have resembled a dire wolf's coat, with visible tufts of grey fur.

Despite its size,