Relationship of baleen whales established by cytochrome b gene sequence comparison.

A recent revision of whale phylogeny suggested that the sperm whale was more closely related to rorquals than to other toothed whales. This made the suborder Odontoceti (toothed whales) paraphyletic, and implied that the latest common ancestor of rorquals and sperm whales may have lived only 10-13 million years ago. This is at variance with palaeontological evidence for the greater antiquity for both mysticetes (baleen whales) and sperm whales, so the Mysticeti, as well as the Odontoceti, must also be paraphyletic if the dates implied in ref. 1 were correct. Here we present a more comprehensive phylogenetic analysis that demonstrates the monophyly of mysticetes and identifies no particular affinity between the sperm whales and rorquals.