Extra sutural bones may also variably be present, but they are not counted.

There may variably also be extra sutural bones present.

Wormian bones, also known as intra sutural bones are extra bone pieces that occur within a suture in the cranium.

It is important to realize that through anatomical variation it is common for the skeleton to have many extra bones (sutural bones in the skull, cervical ribs, lumbar ribs and even extra lumbar vertebrae)