Cetaceans and Hippopotamuses

Whippomorpha is a clade of Artiodactyla that contains all living cetaceans (whales) and Hippopotamidae. This makes it a crown group. Whippomorpha is a suborder within the order Artiodactyla (even-toed ungulates). The placement of Whippomorpha within Artiodactyla is a matter of some contention, as hippopotamuses were previously considered to be more closely related to Suidae (pigs) and Tayassuidae (peccaries). Most contemporary scientific phylogenetic and morphological research studies link hippopotamuses with whales, and genetic evidence has overwhelmingly supported an evolutionary relationship between Hippopotamidae and Cetacea. Modern whippomorphs all share a number of behavioural and physiological traits, such as a dense layer of subcutaneous fat and largely hairless bodies. They exhibit amphibious and aquatic behaviors and possess similar auditory structures.

Whippomorpha is a subgroup of Cetancodontamorpha. Cetanconodontomorpha also includes the more basal extinct helohyids, entelodonts and Andrewsarchus.