Rex Bone Costume

The Rex Bone Costume is dropped by skeletal s during the ARK: Fear Evolved and ARK: Fear Evolved 2 event or crafted in a during the ARK: ARKaeology event. It can be applied to a tamed Rex to make it look like a skeleton.

Obtaining
During Fear Evolved, Alpha T-Rexes will spawn with a skeletal appearance. Killing and looting one of these creatures will yield a Rex Bone Costume The Alpha Skeletal Rex's inventory must be looted by hand in order to get the costume. If you or your mount harvest the corpse, the costume will be lost.

The Rex Bone Costume can also be used to summon s.

This skin can be unlocked by completing the Master Explorer Achievement, after which it will be available in your inventory whenever you respawn.