The Chihuahua molera or open Fontanel is the exact same as the soft spot that a baby has when born. The molera in chihuahuas is not a defect, but a characteristic of the Chihuahua breed. It can vary in size and shape, and is located on the front, top of the head where the bone plates come together.
The chihuahua molera/fontanel is found in a high percentage of toy dogs but most often in Chihuahuas; both smoothcoat Chihuahuas, and longcoat Chihuahuas . The Chihuahua molera is present at birth. Most of the time it will get smaller as the Chihuahua gets older, to about the size of a dime, or it will close completely. Sometimes it will remain with the Chihuahua its entire life. This is not any reason for alarm, the chihuahua will still live a healthy, normal life.