[Pennekamp]

This is definately not an muskrat. The teeth on this animal are of a carnivore. The muskrat is omnivorous, the muskrat skull above shows us clearly that their teeth are mainly for plant material.

NOw, notice the front right leg...it looks as if there is webbing of some kind. So its possible that this "thing" has some aquatic background. I'm guessing it could swim, but the lack of fur would hinder it greatly in that regard. Probably died because of cold temperatures from the water.

In looking closer, there is actually a tail. Which is often used as a rudder.

So my best guess...A semi-aquatic, hairless mammal. Probably a science experiment gone bad.