Some puppies are born with what is called an “open fontanel.” The fontanel is the location on the top of the skull where all of the skull plates join. It is equivalent to the soft spot at the top center of a human baby’s head. When puppies are born, the bony plates of the skull are somewhat soft and separated. As he grows, these bones will become more rigid and will gradually fuse together. It can take two to six months for the skull plates to fuse and the soft spot (fontanel) to close.

In some pups if the fontanel is large, it may take up to 10-11 months for it to close.  In very rare cases, the fontanel never closes.In some breeds, such as the Chihuahua, this open fontanel or molera is actually desired. This means the owner has to be particularly aware as to the sensitivity of this area.