Looks like the front and top part of the skull is missing leaving the bottom, rear portion of the skull where the spinal column is connected. I don't know the species but maybe Harry might know.
Was my first thought , cervid type.
But the lumps on each side (one is shown in last picture near/below to side where spinal column was attached) don't match a deer.
Not sure about jaw hinge area either....
Looks like maybe the rear half of a whitetail deer (or mule deer, blacktail or whatever have you in your area) - missing midway from the eye-orbits forward. Something of known size in the image would help. As would images from the side and top.
Chop this image off at about "G", keeping the upper parts, and there you go.