The atlas! This bone (cervical vertebra 1), named in part after the mythological character Atlas, who carried the world on his shoulders, carries our heads and allows them to move as elegantly, controlled, and precisely as they do.
In real life this vertebra sits high in the neck, just below the base of the skull. Great care was taken to model and create it (although it is just a fraction of real life size!), and to show off all the interesting and unique bony structures on this piece of the spine.
This single pin with 1 pin post needs to be accompanied by a butterfly clasp as can be typically purchased at a craft store.