Sometimes skin is an optional extra

Skin ? It's over-rated. Second photo in the link is truly bizarre.

A newly discovered species of gecko has tearaway skin that leaves predators with nothing but a mouthful of scales when attacked. Many lizards can detach their tails when attacked, but fish-scale geckos have large scales that tear away with ease. The new species is a master of this art, say scientists, having the largest scales of any known gecko.

The skin of fish-scale geckos is specially adapted to tearing. The large scales are attached only by a relatively narrow region that tears with ease. In addition, beneath the scales there is a pre-formed splitting zone within the skin itself. When grasped by a predator, fish-scale geckos lose not just their scales but also the skin underneath.
http://www.bbc.com/news/science-environment-38897327