Any basic head shape can be a dog simply by adding the correct ears and nose. That is really all that Rowlf from the Muppets is.

I've seen a few patterns in the past that create more of a snout but they are not available any more. You might have a look at this tutorial https://www.instructables.com/id/DIY-Dog-Puppet/  over at Instructables. The prairie dog pattern she mentioned is no longer available but on the following pages she uses Bashful puppets round head base and adds to it.