The knob of bone on the front of this skull is a button osteoma. These are small, benign tumors that, though rare, are most commonly found on the frontal or parietal bones of the skull (the forehead or sides). Though small ones can be the size of a pin head and are rarely visible through the skin, larger ones such as this one would cause a distinctive bump that would have been plainly visible in life. As such, they tend to be useful in a forensic context for identifying remains.

Interestingly, this individual had another anomaly as well. The apparent fractured line running up the center of the forehead is actually called a metopic suture. It’s unusual because, though present in children, it usually disappears early in childhood, leaving a smooth expanse of bone. Retaining one through adulthood is rare, though harmless. On the other hand, if this suture closes too early in life the frontal bone will be unable to grow properly, resulting in a deformation called trigonocephaly, so named because the sufferer’s head will have a triangular appearance when viewed from above. Fortunately, this can be corrected surgically if it’s noticed soon enough.