The morbilliviruses recently isolated from two cetacean species in the North and Mediterranean Seas have been shown to differ from phocine distemper virus isolated from European seals using monoclonal antibodies. We have identified a "universal" morbillivirus primer set, based on highly conserved regions of the morbillivirus phosphoprotein (P) gene and used this to amplify a region surrounding the RNA editing site from all known members of the group. Sequence analysis of this region of the gene shows that the dolphin and porpoise viruses are related but quite different from all other members of the group, forming a distinct lineage more closely related to the ruminant morbilliviruses than to the carnivore viruses.