Linnaeus originally assigned the name Cete to the order of mammals consisting of whales, dolphins, and porpoises. The term is derived from the classical noun cetos, meaning a large sea creature. Linnaeus conceived Cete to be the sole member of the group Mutica, one of his three primary subdivisions of placental mammals. The term Cetacea is the plural of cetos and was coined by Brisson in 1762. The study of cetaceans has come to be known as cetology, those who practice it as cetologists.
The lines of demarcation between the living cetaceans and other orders of mammals are firmly drawn, and there is no ambiguity. Similarly, the two living suborders of Cetacea are unequivocally distinct from each other, but also monophyletic; that is, derived from a common ancestor. The Mysticeti, or baleen whales, and Odontoceti, or toothed whales, differ fundamentally in the ways that the bones of their skulls have become “telescoped.” The mysticete skull features a large, bony, broad, and flat upper jaw, which thrusts back under the eye region. In contrast, the main bones of the odontocete upper jaw thrust back and upward over the eye sockets, extending across the front of the braincase. Mysticetes have baleen and no teeth as adults, and they have paired blowholes (nostrils).
Odontocetes, in contrast, have teeth and no baleen (in some species, many or most of the teeth are unerupted and non-
These numbers will inevitably change as larger samples become available and as more sophisticated analytical methods are applied. It is instructive that no less than five “new” species of cetaceans have been described over the past 15 years, including two mysticetes (Antarctic minke whale, Balaenoptera bonaerensis, and pygmy Bryde’s whale, Balaenoptera edeni) and three odontocetes (pygmy beaked whale, Mesoplodon peruvianus, spade-
Vernacular uses of the terms whale, dolphin, and porpoise have always been complicated and, occasionally, confusing. All baleen-
The proclivity of seafarers and fishers to apply the term “porpoise” (singular and plural) to any small cetacean that they encounter has led to its rather loose application to marine dolphins by scientists as well. It is occasionally suggested that porpoises can be distinguished from dolphins by their lack of a pronounced beak (the elongated anterior portion of the skull that includes both the upper and lower jaw), but a number of dolphins are at least as blunt-