Last January (2016), I was in Nuevo Vallarta, Mexico with my family, playing in the waves and looking for shells when I found this little skull.
I have never quite confirmed what animal it came from, but I think (and others have said this as well) that it’s the skull of an axolotl. This seems possible as the axolotl is native to Mexico. It’s kind of sad though because the axolotl is currently critically endangered and possibly extinct in the wild.
I thought it was a really cool thing to find among all the shells and waves. Definitely the best souvenir I’ve ever found.