SPERM WHALE PHYLOGENY REVISITED: ANALYSIS OF THE MORPHOLOGICAL EVIDENCE

Some recent analyses of three mitochondrial DNA regions suggest that sperm whales are the sister group to baleen whales and, therefore, the suborder Odontoceti (toothed whales) constitutes a paraphyletic group. I cladistically analyzed the available morphological data, including that from relevant fossil taxa, for all families of extant cetaceans to test this hypothesis. The results of this analysis unambiguously support a monophyletic Odontoceti including the sperm whales. All synapomorphies that support the Odontoceti node are decisive, not related to the evolution of highly correlated characters, and provide the same result regardless of what order of mammals is used as an outgroup. These numerous, anatomically diverse, and unambiguous characters make this clade one of the best-supported higher-level groupings among mammals. In addition, the fossil evidence refutes a sperm whale/baleen whale clade. Both the molecular and morphological data produce the same unrooted tree. The improper rooting of the molecular tree appears to be producing these seemingly incongruent phylogenies.