Balaena
Whales (Balaena) are a diverse and widely distributed group of fully aquatic placental marine mammals. Within the scientific classification, they fall under the informal and colloquial grouping of large cetaceans, encompassing all members of the infraorder Cetacea except for dolphins and porpoises. However, it is worth noting that dolphins and porpoises can still be classified as whales from a formal, cladistic perspective. From a broader perspective, whales, dolphins, and porpoises belong to the order Cetartiodactyla, which includes even-toed ungulates. Cetaceans, including whales, share a close evolutionary relationship with hippopotamuses and diverged from them approximately 54 million years ago. The two main groups of whales, known as parvorders, are baleen whales (Mysticeti) and toothed whales (Odontoceti). It is believed that these two groups shared a common ancestor around 34 million years ago. Mysticetes comprise four existing families: Balaenopteridae, Balaenidae, Cetotheriidae, and Eschrichtiidae. Odontocetes, on the other hand, include the Monodontidae, Physeteridae, Kogiidae, and Ziphiidae, as well as six families of dolphins and porpoises that are not considered whales in the informal sense.
