Various elements suggest that not only Medusa’s beheading, but also her metamorphosis is present on the parade shield that Caravaggio painted in 1597-1598 and that his patron, Cardinal del Monte, offered to the Grand Duke of Tuscany, Ferdinando de’ Medici. Scholars have recently insisted that the famous rotella shares many features with an engraving by Cornelis Cort, now attributed to Antonio Salamanca, a possible copy of a lost work by Leonardo. Interestingly, this engraving comes with a description of Medusa’s metamorphosis, taken from a passage of Boccaccio’s Genealogy of the Pagan Gods where the Ovidian myth is associated with the legend of the beautiful queen Medusa. Indeed, the Cort-Salamanca’s print shows the metamorphosis in progress: a terrified woman transforming into a monstrous hybrid of humanity and bestiality. While emphasizing the Gorgone’s double nature, Caravaggio pushes her representation in an even more naturalistic direction. Such a naturalization of Medusa, who seems to have lost even her petrifying power, fits with the apotropaic function of the shield as it is exposed in contemporary descriptions of the Grand Duke’s rotella and symbolical interpretations of the gorgoneion.