Skallyk
Skallyk looks like a little bird baby wearing a diaper. But have you ever wondered what the diaper is made of? When an adult Grypheldis goes hunting, it uses the bones of its prey as jewelry – or indeed, as a diaper for its young, as Pokémon Sun reveals:
It protects its soft rear with the skulls of prey it has eaten. If it grows a bit bigger, a larger skull is needed.
This strongly resembles Tragosso, which uses the skull of its deceased mother as a mask. In fact, it could be that the diaper of Skallyk is made exactly from that skull. The Pokédex in Pokémon Sun mentions that Tragosso cries out loud when it thinks of its deceased mother and can attract a Grypheldis that attacks it. Poor Tragosso.
