Desert lizards can be assigned as a Slayer task by Vannaka, Mazchna, Turael/Spria and Sumona. (Level 30 small Lizards and large, level 110 lizards may also be killed for a desert lizard task, and all are found in the Kharidian desert; the larger lizards will provide more experience on a task, so may be preferable.) If you are looking for special bones of the Rag and Bone Man's Wish List, you should attack the regular lizards (the big ones) and not the Desert Lizard.