How does a Duneclaw look like ?
Wookiepedia has this : http://starwars.wikia.com/wiki/Duneclaw
And yes, I remember getting an Codex entry for killing one ... I think it was close to that area which one must go through to get the the Jawa H4 quest - not too far away from Largona. There is also a Datachron in that area, which one can only reach by going through a long, long tunnel (and battling Sandpeople there).