This is a completed action toy designed for collectors.
The hip bone is connected to the leg bone, of course, but when it comes to the mighty Gosei Ground the Gosei Headder connects to the Gosei Groudion, the Sealeon Headder connects to the Gosei Sealeon, and the Skyon Headder connect to the Gosei Skyon. Combined they make the mighty Gosei Ground. Pieces of this robot can also combine with the Leon Laser (linked below).