I have a bit of a question revolving around cubone and marowak,

If cubone wears the skull of its dead mother and later evolves into marowak, It's said that the skull fuses with the pokemon, essentially becoming its new head.

In the anime you can see that the bottom jaw is bone as well.

Does that mean then, that when that marowak dies, the young cubone would be wearing. not the mothers skull but the grandmothers? and the same skull would be passed down generation to generation?