A true scarab rolling dung. This is Phanaeus vindex. Many of the scarabs are dung beetles, as it were. I bet they prefer to be known as scarabs: scarabs that use herbivorous waste. Or something like that. This is a male with that visible unicorn horn. Females have a bigger spoonhead extrusion and no horn. Since it is the female that buries the dung ball and lays an egg on it, I am not sure what this guy is doing. Unless he is rolling around with this hoping to impress a female with the size of his balls. That sounds very possible to me now that I have typed it.

A cleaner (sort of), rounder dung mass, which likely rolls like a bowling ball. I have seen them in the yard making several good feet, hanging on for dear life. This is one of the Canthon species, coppery dung rollers. See the bugguide info here.