Skull and crossbones (Spanish cemetery)

Actual skulls and bones were long used to mark the entrances to Spanish cemeteries (campo santo).

Today, an example of a real skull and crossbones may be seen in the 1732 Nuestra Señora del Pilar church overlooking the famous Recoleta Cemetery in Buenos Aires, Argentina.

The size of these glass window boxes is such that the femurs of the priests thus interred are a bit too long to lie flat and so must be leaned up in an "X" formation.

The Jolly Roger, and the similar Totenkopf was a popular symbol of mortality across at this time across Europe and has its origins in the medieval Danse Macabre.

[1] The Church of St Nicholas in Deptford features two Deaths Heads on its gateposts dating to the early 18th century.