Could this be a Spinone? You decide.

Fresco on the entrance wall of Camera degli Sposi in the Castle at Mantua, Italy. Detail shows Lodovico and grandsons welcoming Cardinal Francesco (Gonzaga); 2nd figure from right may be Mantegna himself. 

The 'typical Spinone head' of the dog portrayed in the Mantegna's picture was admired by breed archivist Adriano Cerasoli in his book published in 1951. It was validated to be an example of the breed by the famous vet and breeder of the Spinone, Doctor Paolo Brianzi.

This is an enhancement from lower left corner 
of the print at left.