(Potamotherium,((Odobenus_rosmarus,(Otaria_byronia,Arctocephalus_pusillus)),((Erignathus_barbatus,(Phoca_vitulina,Halichoerus_grypus)),((Monachus_monachus,Pliophoca_etrusca),((Mirounga_leonina,Callophoca_obscura),((Homiphoca_capensis,(Hadrokirus_martini,Piscophoca_pacifica)),(Acrophoca_longirostris,((Leptonychotes_wedellii,Ommatophoca_rossii),(Lobodon_carcinophaga,Hydrurga_leptonyx)))))))));