Hippopotamus and whale phylogeny.

Abstract in brief

• Thewissen et al. present new fossils from India suggesting that whales and dolphins (Cetacea) are more closely related to an extinct group called Raoellidae, and that hippopotamuses are more closely related to pigs and peccaries (Suina) than to whales.
• Our reanalysis, which kept more molecular data, shows that hippopotamuses are actually the closest living relatives to whales and dolphins, fitting with earlier studies.
• This supports the idea that both hippopotamuses and cetaceans inherited their aquatic features from a common ancestor, rather than hippopotamuses being more closely related to pigs.