Chaotic Gore Magala is a rare special Gore Magala individual that has failed to molt properly into a Shagaru Magara and has only molted half way on one side of its body. It also has a different music theme which has parts of Gore Magala's and Shagaru Magara's respective theme music. This variant of Gore Magala first appeared in Monster Hunter 4 Ultimate with a separate Icon, yet in game it does not have a separate name from an ordinary Gore Magala.
Source: http://monsterhunter.wikia.com/wiki/Monster_Hunter_Wiki