User blog comment:Kogath/Monster Hunter X Discussion/@comment-10613301-20150922204847/@comment-184612-20150922205655

Actually, if you look closely, they're modeled after the gen the location they come from represents.

Raisekusu = 1st gen

Gamuto = 2nd gen

Tamamitsume = 3rd gen

Dinovaldo = 4th gen

The art team really paid attention to minor details like this.