Considering that the average weight of a male coyote is about 35 lbs, you can certainly understand why I'd be skeptical of any claim of abnormally large coyote being somewhat common. Feral dogs, after several generations of crossbreeding, often begin to assume features of wolves all the breeds are derived from, so if there is a well established population of multi-generation feral dogs they might be confused with their wild cousins. There are distinct differences between dogs/wolves and coyote, but to be sure you'd have to have a necropsy done.
But until proven otherwise, I'll take your word for it that what you have was a true coyote.
Mike