 The traditional view has been that Mysticeti ( baleen whales ) and Odontoceti ( toothed whales ) arose from more primitive whales early in the Oligocene period , and that the super @-@ family Physeteroidea , which contains the sperm whale , dwarf sperm whale , and pygmy sperm whale , diverged from other toothed whales soon after that , over 23 million years ago . From 1993 to 1996 , molecular phylogenetics analyses by <unk> and colleagues , based on comparing the genes of various modern whales , suggested that the sperm whales are more closely related to the baleen whales than they are to other toothed whales , which would have meant that Odontoceti were not monophyletic ; in other words , it did not consist of a single ancestral toothed whale species and all its descendants . However , more recent studies , based on various combinations of comparative anatomy and molecular phylogenetics , criticised <unk> 's analysis on technical grounds and reaffirmed that the Odontoceti are monophyletic . 
