I dubbed this guy the North Rim Miniature Great Horny Toad. It turns out I was not too far off: he seems to be a Mountain Short-Horned Lizard (Phrynosoma hernandesi). According to Wikipedia, they eat mostly ants, and squirt blood out of their eyes if threatened by canids (dogs, wolves, coyotes, foxes, etc.). All this one did was run around so that I could not focus properly.