Fox or Dog ? The species are closely related, but the variety of sizes and shapes of domestic dog means that simple measurements or features to separate them are difficult to find. Perhaps the most reliable feature is the "inflated" sinuses of the frontal bones in dogs.
In Europe, a medium-sized, dog-like skull with flat or concave surfaces to the post-orbital processes and only very slight inflation of the frontal sinuses is probably a fox.
Other fox species illustrated on this site: arctic, bat-eared, fennec, gray, kit, swift.