Of note, the tail connector piece on his back is a painted die-cast strip. The other Fossil Lords featured unpainted die-cast, so it is good to see that the designers were still willing to paint the metal where needed (in this case, to stop the alternate mode from having a silver stripe down its back). His most obvious feature is his tail. I had spent time writing how his tail dangles from his back, but just discovered a step in his transformation that the instructions don't make clear - the die-cast strip pushes up into his back, hoisting the tail up and locking it in place. It's amazing how there are always new things to discover in the world of Rock Lords!
Tailbone is a limited figure, and seems to have got the tail-end (pun intended) of the figure's design budget. He's a lot simpler and more basic than the other figures, and just does what he needs to do - ie turn into a tail. Yes, he has his issues (especially that the arms go nowhere when he transforms) but there something about his chunkiness that makes me prefer him to some of the more complex Fossil Lords.