Sutural bones of the cranial vault are formations associated with insufficient rate of suture closure, and regarded as epigenetic and hypostatic traits. These bones rest along sutures and / or fill fontanelles of the neonatal skull. We found a case of an unusual sutural bone, in the region of the bregmatic frontanelle. This sutural bone was tetragonal and remarkably large. This case displays the possibility of discrete diversification of the ossification centres, as well as the relative stability of the structural skull matrix in response to discrete changes. Knowledge of this variation is very important for anthropologists, radiologists, orthopaedic and neuro-surgens.