A cladistic analysis that includes representatives of all recent genera of mysticetes and several fossil species that

were previously referred to the family Cetotheriidae, with tooth-bearing mysticetes and an archaeocete as an outgroup,

is presented here. The result of this analysis forms the base of a revised classification of Mysticeti. Cetotheriidae

is redefined as a monophyletic family, which includes the genera Cetotherium, Piscobalaena, and a new

subfamily Herpetocetinae, including Herpetocetus, Nannocetus, Metopocetus, and Cephalotropis. Eschrichtiidae is

the closest sister taxon to Cetotheriidae. A few species are referred to Eomysticetoidea, whereas the remaining species

that were previously referred to Cetotheriidae appear in four clades that branch off from the lineage leading to

Balaenopteridae. These are a Mauicetus clade and three clades that are named as new families Aglaocetidae,

Pelocetidae, and Diorocetidae