Cryptid Canines: Unknown Predators?

This is one of my favorite topics in cryptozoology: I'm not sure why, since the evidence is pretty thin, but maybe I just like dogs and wolves and doglike critters. Karl Shuker writes here of some predators reported across North America, from New Mexico to Greenland. They form a mixed bag of real wolves, spirit wolves, and something called the waheela which has been labeled a dire wolf (Canis dirus) or an amphicyonid, or "bear-dog," which is a really fierce-looking creature kind of like a short-legged wolf after some serious steroids and weight-lifting.  To add confusion, there is the wolf-like, or maybe hyena-like, Shunka Warakin, a stuffed specimen of which has actually turned up, but I can't find any report that testing has been completed.  Chad Arment, in his book Varmints, also chronicles some weird sightings of a scary carnivore from Arkansas.  To summarize, some of these look like giant wolves, some like much more robust canids, and some barely like canids at all.
There may be nothing unusual behind all this business. After all, humans just about wiped out the known wolves, so it's problematical that larger relations could have survived.  But I'm not quite ready to write off all the creatures of this type.  All you need is one big, really remote valley....