How can I mount a Dino head to a wall?
I don't have this particular piece but my advice for most 'non-standard' connections such as these is to use a part that is flexible enough to fit the gap. 

The 'Technic, Axle Connector Double Flexible' piece under compression can make a snug enough fit to mount a sharks head. 

In this example, you can use two Technic Axle-Pin attached to another two Technic 1X1 bricks.







If you turn the rubber brick 90 degrees on it's side and place two of them together you might be able to attach something that isn't as wide.