Skeleton Archers are Undead.
The basic bones with a bow, skeleton archers return for their third go 'round in the Diablo series, and they are much as they've ever been. A humanoid skeleton with a bow and a relatively slow firing rate. They are not dangerous one on one, but a pack of them can be pretty nasty, especially against low armor or stationary targets.
In Diablo III they usually spawn with Skeletal Shieldman, firing from the relatively safety they find behind their blocking brethren.