Board Thread:Pokemon Arena X- CAMP/@comment-5398529-20140219084135/@comment-5398529-20140220011146

From Bulbapedia:

"Originally, according to interviews with Ken Sugimori in Nintendo Dream, Hydreigon and its pre-evolutions were intended to be cybernetic dragons incorporating aspects of tanks within their bodies before being redesigned around the theme of Yamata no Orochi. The tank track-like markings on Hydreigon's body are a remnant of this design."