This critter is called a Seeping Sand Creature. It oozes acid-blood out of it's butt/back/tail pores. It lives in the Night-Desert. It is both predator and prey, but judging by those teeth, it probably preys upon others more than it's preyed upon.

The design for this was inspired by a contest over at DeviantArt. The topic was 'Buttock Defense'. (Little in the middle, but she's got much back! :D and check out that grill! lol) More concept sketches of this critter can be seen here.