Hesperocyon gregarious was a species of dog that lived during the Eocene and Oligocene epochs. It first appeared roughly 42 million years ago. Hesperocyon is an important animal, in that, it is the first true dog that is known to science. So all those little doggie buddies that some of us have can trace their roots back to this animal
Here is a picture of a hesperocyon skull. The whitish area is what was exposed when found and bleached by the sun. This skull would be from an adult animal and should give you a good idea of the size of these first true dogs
Here is the other side of the skull. There are a few tortoises in the back ground.
