Proteins can undergo a diversification of functions by means of duplication events and neofunctionalisation. Sodefrin Precursor Factor (SPF) is a protein so far described only in salamanders, which has two pheromone functions. We propose here the hypothesis of an SPF diversification of pheromone and defensive functions. To unravel structural and functional evolution of SPF in amphibians, new precursors are first identified using transcriptoomanalyses. An evolutionary reconstruction of the SPF system on the basis of the identified proteins and SPF-precursors, and the functional variation observed in the model species, will be made. Evolutionary changes in SPF-diversity, structural changes and functional shifts will be reconstructed on recently published phylogenetic trees for amphibians.