Skull

From DwarfFortressWiki

Skulls can be obtained from the corpses of dead creatures and as a by-product of butchering.

Skulls can be processed into totems at the craftsdwarf's workshop.

Unlike bones or shell, dwarves never request skulls for strange moods.

For totems, the value of the skull is very important. Like all creature byproducts, the skull value is scaled by the modvalue of the creature.